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Lysozyme: Antibacterial Enzyme and a Cause of Egg Allergies

Linda Crampton is an experienced teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.

Lysozyme is an antibacterial enzyme that is present in human body secretions and fluids and in egg white.

Lysozyme is an antibacterial enzyme that is present in human body secretions and fluids and in egg white.

Functions and Uses of Lysozyme

Lysozyme is an antibacterial enzyme found in body secretions, including saliva, mucus, tears, and human milk. Enzymes act as catalysts for chemical reactions. The activity of lysozyme is part of our body's first line of defense against invading microbes. The substance is very helpful in areas that aren't protected by a skin barrier.

Lysozyme is also a component of egg white, where it helps to protect the environment around the developing chick. In addition, it's added to certain foods, medications, and vaccines as a preservative. Commercial lysozyme is generally obtained from egg white. Unfortunately, some people are allergic to the enzyme. It's one cause of egg allergies.

Alexander Fleming's Discovery of Lysozyme

The discovery of lysozyme may be a great example of serendipity in science. Serendipity is the act of making an unexpected or fortunate discovery while searching for something else. The enzyme was found by Alexander Fleming (1881–1955). He later discovered penicillin, an antibiotic of great importance.

At the time of his lysozyme discovery, Fleming was involved in studying microorganisms. He was known as an untidy scientist. His laboratory was filled with Petri dishes containing microbes growing on agar. (The term "Petri dish" is capitalized because it's named after a bacteriologist named Julius Richard Petri.) The dishes were piled on lab benches in a seemingly disorganized fashion. Fleming's collection actually helped him with his discoveries, however.

One day in 1921 when Fleming had a cold, a drop of mucus fell from his nose on to a Petri dish that he was examining. Although most accounts describe this event as accidental, which makes a nice story, Fleming may have deliberately added mucus to the dish out of curiosity.

Bacteria cultures were growing on the nutrient agar in the Petri dish that Fleming was examining. Agar is a jelly-like substance obtained from algae. When nutrients are added to agar, it becomes a good growth medium for bacteria. Fleming discovered that the bacteria around the mucus drop in the Petri dish died. After further investigation, he realized that a protein in the mucus was responsible for the death of the bacteria. Enzymes are a type of protein. Fleming named the protein in the mucus lysozyme.

The word lysozyme comes from "lysis", which is the process in which a cell bursts, and "enzyme", which is a protein that causes or speeds up a chemical reaction.

Gram Staining Method of Classifying Bacteria

Lysozyme destroys only Gram-positive bacteria, but it's still useful. Bacteria are categorized into two major groups based on their reaction to specific stains. The technique is known as the Gram staining process. The classification method was created in 1884 by Hans Christian Gram, a Danish scientist, which is why the word "Gram" is generally capitalized. After the staining process has been performed, Gram-positive bacteria have a purple cell wall and Gram-negative bacteria have a pink one.

The relative thickness of the peptidoglycan layer in the outer covering of bacterial cells produces the different colours when the stain is applied. Gram-positive cells are covered by a cell membrane that is in turn covered by a thick cell wall made of peptidoglycan. Gram-negative cells have an inner cell membrane, a thin peptidoglycan cell wall, and then another membrane on their outer surface.

Peptidoglycans in the Cell Wall of a Bacterium

Lysozyme breaks some of the bonds between the peptidoglycans in the bacterial cell wall.  NAG stands for N-acetylglucosamine and NAM stands for N-acetylmuramic acid.

Lysozyme breaks some of the bonds between the peptidoglycans in the bacterial cell wall. NAG stands for N-acetylglucosamine and NAM stands for N-acetylmuramic acid.

How Does Lysozyme Destroy Bacteria?

One of the bacterial wall's jobs is to withstand the pressure created by the fluid inside the cell and to keep the cell intact. Lysozyme breaks some of the bonds that hold the peptidoglycans in the wall together. As a result, the wall weakens and the bacterium bursts.

Lysozyme is effective against Gram-positive bacteria and not Gram-negative ones because the outer membrane of the latter cells helps to protect them from the enzyme. In Gram-positive cells, lysozyme can immediately get to work destroying the peptidoglycan layer in the cell wall. Despite the limited action of the enzyme, it's a valuable part of the immune system.

Some people are allergic to the lysozyme in chicken eggs.

Some people are allergic to the lysozyme in chicken eggs.

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Read More From Youmemindbody

Egg Allergy

The human immune system is complex, fascinating, and awesome. It normally does a wonderful job of protecting us from the potentially dangerous microbes that we are exposed to every day. Sometimes the system needs help in the form of prescribed medications, however. In some people, it makes a mistake and attacks a substance or material that isn't a threat to the body.

When someone has an egg allergy, their immune system mistakenly attacks one or more proteins in eggs, producing an allergic response. In this type of response, the system overreacts to a harmless stimulus. Egg yolk and egg white both contain proteins. Since the proteins are more abundant in the white, this part of the egg is usually the cause of an egg allergy. Lysozyme is one protein in egg white that can trigger an allergic response.

An Allergist Discusses Egg Allergies

Possible Symptoms of the Condition

Symptoms of an egg allergy range from mild to serious. Sensitive people may experience one or more of the following symptoms after eating or even touching eggs:

  • skin rash
  • hives
  • runny nose
  • sneezing
  • wheezing
  • difficulty in breathing
  • stomach pain
  • nausea
  • vomiting
  • diarrhea

Anyone who experiences symptoms such as those listed above should see their doctor to get a diagnosis and treatment advice.

Egg allergies are more common in children than in adults. The American College of Allergy, Asthma and Immunology says that 70% of children with an egg allergy no longer have the allergy by the time they reach the age of 16. Sometimes an allergy persists into adulthood, however. It may even appear for the first time when a person is an adult. This variation in the allergy's presence is why the questions in the egg allergy poll below refer to both the past and the present.

An Egg Allergy Survey

Egg Substitutions for Baking

Anaphylaxis Facts

An uncommon but very serious result of an egg allergy is anaphylaxis, which can sometimes develop rapidly. Anaphylaxis is a body-wide allergic reaction that involves a dramatic drop in blood pressure, severe difficulty in breathing, and sometimes loss of consciousness. The condition is life threatening and is a medical emergency.

People with a severe allergy may be prescribed an epinephrine auto-injector. They must carry this around with them in case they are accidentally exposed to an allergen, such as components of eggs. Epinephrine is a hormone that expands the airways, making breathing easier, and constricts blood vessels, counteracting the drop in blood pressure. The hormone is also known as adrenaline.

Lysozyme Allergy

Egg white allergies are often caused by a protein other than lysozyme. These proteins include ovalbumin, ovotransferrin, and ovomucoid. Nevertheless, allergies to lysozyme from egg white do exist.

If someone is allergic to lysozyme, they will have to do more than simply stop eating eggs. Lysozyme from hens' eggs is added to many prepared foods as well as to some types of wine, some medications, some influenza (flu) vaccines, and the yellow fever vaccine. The ability of the enzyme to destroy many bacteria makes it a good preservative in these products. In addition, any food with added eggs or egg whites contains lysozyme.

Anyone with a lysozyme allergy should check the ingredient list on a package of prepared food carefully or check with the product's manufacturer to ensure that the enzyme is absent. One problem with checking ingredient lists is that manufacturers may not be required to list lysozyme as an ingredient if it's present in a very small concentration. This may not matter in someone with a mild allergy, but it could be very important in someone with a severe one.

If someone is allergic to a component in a vaccine, this doesn't necessarily mean that the person should refuse to be vaccinated. It would be a good idea to receive the vaccine in a medical facility containing emergency medications and equipment instead of in a pharmacy or a workplace, however. As always, a doctor should be consulted about medical matters.

Albumen is another name for egg white. The word shouldn't be confused with ovalbumin, which is the most abundant type of protein found in the white of an egg.

Cooked and Separated Eggs

Some people may be allergic to the lysozyme in uncooked eggs but not to the enzyme in eggs that have been cooked for a long time at a high temperature. Nobody with a severe allergy should experiment with this idea outside of a medical setting, however.

Another possibility is that someone who is allergic to lysozyme but to none of the proteins in egg yolk may be able to eat the yolks of eggs. This is unlikely, however, because it's almost impossible to completely separate an egg yolk from the egg white. It definitely shouldn't be attempted in someone with a severe egg allergy.

Lysozyme is present in the white of an egg.

Lysozyme is present in the white of an egg.

Unboiling an Egg

Lysozyme is involved in a process that sounds amusing but could have practical importance. Strange as it may sound, in 2015 scientists discovered how to unboil an egg—or in other words, how to change the solid egg white of a boiled egg back into a liquid again. Specifically, they learned how to obtain normal and usable lysozyme from cooked egg white.

Egg white is rich in proteins, which are made of chains of amino acids. The chains are folded into complex shapes. The shape of a protein is vital to its function. If the protein is misfolded or changes its shape, it can no longer do its job. This is a very serious condition inside the human body, which contains many vital proteins.

During boiling and some other stresses, proteins are denatured. "Denaturation" means a change in shape. Chemical bonds holding the protein chains in the correct shape are broken. The chains then unfold and become tangled. This process is responsible for egg white changing from an almost colourless liquid to a white solid when it's boiled or otherwise cooked.

The procedure for recycling lysozyme from cooked egg white was developed at the University of California, Irvine. The process is surprisingly quick and easy. It requires minutes to complete, compared to an older method that requires days.

In their experiment, the researchers added a chemical called urea to cooked egg white, which turned the white into a liquid. They then put the liquid in an instrument called a vortex fluid device, which applied shear stress to the egg white proteins. As a result, the lysozyme chains in the egg white untangled and refolded correctly.

Uncooked egg white changes its appearance during heating due to denaturation.

Uncooked egg white changes its appearance during heating due to denaturation.

The Significance of Untangling Lysozyme

The value of the discovery described above is not that an egg can be unboiled, which might seem like an unnecessary action. Instead, its value lies in the fact that it demonstrates that the tangled amino acid chains of lysozyme—and perhaps the tangled chains of other proteins—can be quickly returned to their normal state. This could have valuable applications in both industry and medicine.

Lysozyme is an interesting and useful enzyme. Studying the protein and its behavior could have important benefits for health and may also help us to better understand the fascinating world inside the human body.

References and Resources

  • Alexander Fleming, lysozyme, and penicillin from the NIH (National Institutes of Health)
  • The American College of Allergy, Asthma and Immunology website has more information about egg allergies.
  • This Mayo Clinic web page lists the major allergenic proteins in eggs and gives suggestions for preventing egg allergy symptoms.
  • An allergy to eggs is described in an article from the Pediatric Clinics of North America journal
  • Information about unboiling an egg is provided by the University of California, Irvine website.

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2015 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on April 03, 2018:

I eat quite a lot of eggs, too. It would certainly be awkward to be allergic to them. Thanks for the visit, Mary.

Mary Norton from Ontario, Canada on April 03, 2018:

Thanks again for the education. I would be very sad if I have egg allergy. As a child, this was mainly what I ate as I did not like many things.

Linda Crampton (author) from British Columbia, Canada on November 23, 2016:

Hi, Suzanne. Yes, lysozyme is produced in the body. Its function is to fight bacteria rather than intolerance. It would be a good idea to ask a doctor to explain the result of your test.

Suzanne on November 23, 2016:

Hi I was googling Lysozymes in an effort to find out if having a high Lysozme count in an acids test would mean one had an intolerance to egg white.

After reading your interesting article i think it says the Lysozmes are natural in a persons body and are just released as a defensive reaction any type of intolerance reaction , so not necessarily related to egg white itself.

Is that correct? Many Thanks Suzanne .

Linda Crampton (author) from British Columbia, Canada on March 30, 2016:

Thank you very much. Flourish! I appreciate your visit.

FlourishAnyway from USA on March 30, 2016:

I'm back to say Congratulations on HOTD!

Linda Crampton (author) from British Columbia, Canada on March 30, 2016:

Hi, Kristen. Thanks for the congrats and the kind comment!

Linda Crampton (author) from British Columbia, Canada on March 30, 2016:

Thank you very much for the comment, Kimberleyclarke. I agree we you - sometimes we definitely do know what's best for our body!

Kristen Howe from Northeast Ohio on March 30, 2016:

Linda, congrats on another HOTD! This was another remarkably interesting hub dealing with egg allergies. This was another great hub to read.

Kimberley Clarke from England on March 30, 2016:

Fantastic article, thank you. I stopped eating eggs a long time ago - I would always get nauseous after eating them. I never had this diagnosed - sometimes you know what is best for your own body! This article has helped me to understand my egg sensitivity better.

Linda Crampton (author) from British Columbia, Canada on March 09, 2015:

You're welcome, Huntgoddess. Thanks for the visit.

Huntgoddess from Midwest U.S.A. on March 09, 2015:

Thanks, Alicia. Thanks, Larry.

The topic is very interesting. I do have some vegan friends, so I want to keep on top of things, even though I am no longer vegan myself.

Linda Crampton (author) from British Columbia, Canada on March 07, 2015:

Thank you very much for the kind comment, Deb!

Deb Hirt from Stillwater, OK on March 07, 2015:

Wow, fascinating is right! I love your science reports, they really show me how more things work.

Linda Crampton (author) from British Columbia, Canada on February 06, 2015:

Thank you very much for the comment, Flourish. I appreciate the vote and the pin, too. We do seem to be hearing a lot more about allergies today. I'm sorry about your nut allergy. That must require a lot of caution.

FlourishAnyway from USA on February 06, 2015:

Unboiling the egg is a mindblowing concept, one I certainly never heard of. And I never never considered just how dangerous an egg allergy could be. I'm allergic to nuts and have had pretty serious reactions from pecans but it sounds like eggs are a very serious matter given their role in vaccines. We just never used to hear so much about allergies like we do now. Awesome hub! Voted up and more and pinning.

Linda Crampton (author) from British Columbia, Canada on February 05, 2015:

Hi, Huntgoddess and Larry. You've both raised good points. I agree with you, Larry. A vegan would definitely have to do research to ensure that they are get all the nutrients that they need, including Vitamin B12 and the best forms of omega 3 fatty acids. I know that there is now an algal source of DHA (one of the omega-3 fatty acids found in some fish) which I would definitely take if I became a vegan. Life does seems to be getting easier for vegans.

Larry Fields from Northern California on February 05, 2015:

Hi Alicia and Huntgoddess,

The conversation-stopper about Veganism is Vitamin B-12. At the moment, it is not possible to get this nutrient from plant-based sources. However you can get B-12 from supplements, whose contents come from bacteria raised in stainless steel vats, or from vitamin-fortified foods. Example: certain cold breakfast cereals.

Back in the bad old days, almost all non-cheating Vegans earned Darwin Awards. However in principle, a Vegan could get adequate B-12 from thoroughly boiled swamp water. Why? Because various animals 'make use' of the swamp. Bon appetite.

And yes, a certain seaweed can 'test positive' for B-12. So what?

People who have never consumed recreational chemicals sometimes test positive for one or more of these. Employers sometimes fire people because of things that show up on an el cheapo TLC plate, which is intended to be a preliminary screening tool. And they don't bother to follow up with a more accurate and more expensive test. The same principle applies to seaweed that 'tests positive' for B-12.

If you want to be be a healthy Vegan, you need to be scientifically literate. There are secondary nutrient issues, in addition to B-12. Meat-is-murder propaganda is no substitute for homework, coupled with well-honed analytical abilities.

On the whole, Vegans are less healthy than Lacto-Vegetarians. But LVs tend to be healthier than American omnivores. Is this second inequality true, because meat and/or factory farming are inherently 'evil'? I doubt it.

LVs tend to eat more fruits and veggies than omnivores, and these foods contain various healthful micronutrients. Example: the anti-carcinogen, lycopene, in tomatoes.

Huntgoddess from Midwest U.S.A. on February 05, 2015:

Yes, true, I also do love animals. Some of these local farmers have won humane awards for treating the animals well.

I'm sure I could have and should have been much smarter back then, about a better way to do it properly, without compromising my own health.

Yes, there are nutrients that are missing or more difficult. I like the compromise idea, though. It never hurts to learn as much as possible.

Thanks again, Alicia.

Linda Crampton (author) from British Columbia, Canada on February 05, 2015:

Veganism appeals to me very much, since I'm an animal lover and hate the horrors that are frequently part of factory farming. I've heard about other people with health problems that appear after following a vegan diet, however. Certain nutrients would be harder to obtain in the diet. I try to compromise, as you do, Huntgoddess.

Huntgoddess from Midwest U.S.A. on February 05, 2015:

Thanks, Alicia. After a while, I realized that I wanted to be vegan primarily because of all the problems with factory farming, but then I realized there were local farmers who sold grass-fed meat that is healthy and humane.

So, now I buy that, and stay away from factory farming --- whenever possible.

I lost my gallbladder and three teeth to veganism :-(( I think I probably should have at least added cheese and eggs.

Thanks for your comment.

Linda Crampton (author) from British Columbia, Canada on February 05, 2015:

Hi, Huntgoddess. Thank you very much for the comment. It was interesting to read about your personal experience with veganism.

Huntgoddess from Midwest U.S.A. on February 05, 2015:

Ok, thanks for the info, Alicia. I will tell anyone who needs to know.

I tried to be vegan once, a long time ago, for several years. I never really could find an adequate substitute for eggs in baking. (Or anything else, really. I had major health problems back then. I don't think I will ever want to be vegan again.)

Linda Crampton (author) from British Columbia, Canada on February 05, 2015:

Thank you, drbj. I appreciate your visit!

drbj and sherry from south Florida on February 05, 2015:

Thanks, Linda, for adding to my knowledge about Fleming and his discoveries. I knew of Penicillin, but Lysozyme? Who knew? ;)

Linda Crampton (author) from British Columbia, Canada on February 05, 2015:

Thank you very much for the visit and the comment, Pamela.

Pamela Oglesby from Sunny Florida on February 05, 2015:

Excellent information for people with egg allergies. I liked the information about Fleming also. Very useful and interesting article.

Linda Crampton (author) from British Columbia, Canada on February 04, 2015:

Thank you so much for the kind comment and for sharing the interesting information, Larry. I appreciate the votes, too. I like some of the fake ice creams as well. Cherry chocolate chip sounds like a delicious flavour.

I'm eagerly awaiting the discovery of how to put toothpaste back into the tube!

Larry Fields from Northern California on February 04, 2015:

Hi Alicia,

This outstanding hub is informative, well researched, and well-written. Voted up and much more.

I have numerous allergies and food sensitivities -- including eggs, which I can eat in small quantities as minor ingredients in other foods. Otherwise, I feel out of sorts.

About ice-cream . . . I have issues with the quantity of milk proteins that goes into regular IC, but not with butter, which is arguably the finest taste in the universe. I like the fake IC from Trader Joe. Their best flavor is cherry chocolate chip.

About unboiling an egg . . . A better trick would be to put the toothpaste back into the tube.

Linda Crampton (author) from British Columbia, Canada on February 03, 2015:

Thank you, Peggy. I appreciate the comment very much.

Peggy Woods from Houston, Texas on February 03, 2015:

Hi Linda,

I did not realize until talking one day to my cousin on the telephone that he is allergic to eggs. I think that he will find this of interest as well as others reading this informative hub. Thanks for writing it!

Linda Crampton (author) from British Columbia, Canada on February 03, 2015:

It certainly would! There are egg substitutes that can used in baking, though, like the ones shown in the second video in this hub. They would be very useful for someone with an egg allergy.

Huntgoddess from Midwest U.S.A. on February 03, 2015:

Glad to hear that. No pancakes, crepes, etc.

That would be horrible!

Linda Crampton (author) from British Columbia, Canada on February 03, 2015:

Hi again, Huntgoddess. No, I'm happy to say that I'm not allergic to eggs!

Huntgoddess from Midwest U.S.A. on February 03, 2015:

I see. Well, you know a lot, at any rate.

Yes, I also think I am not allergic to them.

I hope you are not allergic? That would be very sad.

Linda Crampton (author) from British Columbia, Canada on February 03, 2015:

Hi, Huntgoddess. I'm a biology and chemistry teacher, not a chemist. I would say that you probably aren't allergic to eggs if you love them and can eat them with no problem! Thank you for the visit and the votes.

Huntgoddess from Midwest U.S.A. on February 03, 2015:

I am really confused now!

You must be a chemist, right?

Well, I love eggs, so I'm guessing I do not have an allergy?

Up, interesting --- even though I really don't understand very much. I'm trying, though. LOL

Linda Crampton (author) from British Columbia, Canada on February 03, 2015:

Hi, Nell. Thanks so much for the comment, the vote and the share. I always appreciate your kindness!

Nell Rose from England on February 03, 2015:

Fascinating stuff Alicia, I didn't realise it was also in saliva, and no I have never had an egg allergy. always love your hubs, I learn something new! voted up and shared, nell