Egg Allergy and Medication: Egg Lecithin, Lysozyme, and the Propofol Question

Egg turns up in only a few medicines, and the most famous is propofol, a widely used anesthetic made with egg lecithin and soybean oil. If you or your child has an egg allergy, you may have heard that propofol is off-limits. The American Academy of Allergy, Asthma and Immunology (AAAAI) says otherwise: people with egg allergy can receive it without any special precautions. The reason comes down to what an egg allergy actually is, and there is one detail your anesthesia team should always hear from you.

The propofol question

Propofol is an intravenous medicine used to put people to sleep for surgery and other procedures, and to sedate some people on ventilators. It is given as a fat emulsion: the drug is mixed into a liquid containing soybean oil and egg lecithin, a purified fatty substance from egg yolk. On the label, the egg ingredient may appear as purified egg phospholipids.

That egg ingredient is where the reputation comes from. The prescribing information for some versions of propofol lists a history of anaphylaxis to eggs, egg products, soybeans, or soy products as a reason not to use it. Egg allergy has long been cited as a reason to avoid propofol, and in some hospitals the practice has been to choose a different anesthetic for anyone with an egg allergy, a practice one Danish research team concluded is not evidence based.

What the allergy specialists say

People with a food allergy are allergic to proteins in the food, not to its oils or fats. Egg lecithin is a purified fat-like substance from egg yolk. The AAAAI notes that it may contain trace amounts of residual protein, but that no allergic reactions have been demonstrated to be caused by this.

Propofol can cause allergic reactions. But the AAAAI points out that most reports of anaphylaxis to propofol have occurred in people without egg allergy, that the vast majority of people with egg allergy receive propofol without a reaction, and that people who react have usually been given other drugs at the same time that can cause or worsen anaphylaxis, such as antibiotics, muscle relaxants, and narcotic pain medicines. Its bottom line: patients with egg allergy can receive propofol without any special precautions, and anyone who has an apparent allergic reaction to propofol should be evaluated by an allergist.

Research in children points the same way, with one caveat that lines up with the label. An Australian hospital review of egg-allergic children who received propofol found a single non-anaphylactic reaction, in a child who had a past anaphylaxis to egg. The authors concluded that propofol is likely safe for most egg-allergic children who do not have a history of egg anaphylaxis. That history is the detail to pass on.

Egg lecithin in IV nutrition

The same ingredient shows up in intravenous fat emulsions, the part of IV nutrition that supplies fat to people who need nutrition by vein, often in the hospital. These emulsions contain egg-yolk phospholipids, and egg allergy is listed as a contraindication in their labeling. Reactions are uncommon, but they are not unknown: a published case described a 2-year-old with an undiagnosed egg allergy who developed widespread itching on IV nutrition that resolved only when the fat emulsion was stopped.

As with soybean oil, which our soy guide covers, an ingredient that goes straight into a vein is a different conversation from the same ingredient in a pill. These are hospital decisions made with you, not choices you face at the pharmacy counter, so the most useful thing you can do is make sure the team knows about the allergy.

Lysozyme: an egg-white enzyme in some medicines abroad

Lysozyme is an enzyme that can be taken from hen egg white, and unlike lecithin it is an egg protein and a recognized egg allergen. Up to 32% of people with egg allergy are sensitized to it. In some places, including Singapore, it has been sold in over-the-counter mucus-thinning medicines, and reactions including hives, swelling, and anaphylaxis have been reported. Singapore phased lysozyme out as a therapeutic product by the end of 2018. If you buy cough or cold medicine abroad, or receive an imported product, look for lysozyme (sometimes lysozyme chloride) on the label.

Vaccines are a separate question with their own guidance: the CDC says people with egg allergy may receive any flu vaccine that is otherwise appropriate for their age and health.

How to check a medication for egg

• Read for the names: egg lecithin, egg phospholipids, and lysozyme in the inactive ingredients.
• Before any procedure, tell the anesthesia team about the egg allergy and any history of anaphylaxis, and let them decide on the anesthetic.
• After a reaction to any medicine, see an allergist to sort out the cause. Our guide to whether you are allergic to the drug or the filler explains why an inactive ingredient can be the culprit.
• For children, make sure the egg allergy is on every chart and pharmacy profile. Our guide to allergy-safe medicine for kids covers what to ask.
• Do not stop anything on your own. Review any concern with your prescriber or pharmacist.
• Check the product with the app. AllergenMeds flags egg-derived ingredients in the exact product you look up, so you know what to confirm.

This guide is for education only, not medical advice. Always talk to your doctor or pharmacist before starting, stopping, or switching any medication.