We have been writing about tick bite meat allergy for years. This reader describes it, and offers a new dietary caution:

“I have alpha-gal syndrome (AGS), which is an allergy to red meat (beef, pork, lamb, venison) and other products that are mostly derived from nonprimate mammals (butter, milk, gelatin, collagen, etc.) and to additives such as carrageenan.

“The condition typically begins with a tick bite. Ticks carry alpha-galactose molecules from the blood of the animals they have previously bitten, such as cows, deer or field mice. When the tick bites a human, it injects the alpha-galactose in its saliva into the person’s body.

“In some people, the injected saliva triggers an immune system response that later produces mild to severe allergic reactions after ingesting red meat or carrageenan (derived from seaweed). Signs and symptoms of AGS can include the following: hives, swelling of the lips, face, tongue or throat, wheezing, stomach pain, diarrhea, nausea, vomiting, headaches or anaphylaxis. “The best course of action is prevention by avoiding red meat and other suspect items. AGS can occur in response to carrageenan used as a food additive, intravenous administration of gelatin-based plasma volume expanders and vaccines.

“I have had a couple of mild AGS flareups despite eating what I considered to be a clean diet. I traced these reactions to eating some vegan hot dogs that contained collagen in the casings and to carrageenan added to the basting sauce for rotisserie chicken. (I usually can eat poultry and fish without incident.) My curiosity spurred research about the adverse effects of carrageenan because it’s derived from a plant and therefore the odd one out in a long list of mammalian products that can prompt an AGS reaction.

“Carrageenan is used as an additive to thicken, emulsify and preserve foods and drinks. It is extracted from edible red seaweeds.

“People should read labels carefully to avoid carrageenan. Manufacturers use it in vegan and vegetarian products to replace gelatin, which is made from animal parts.

“Common sources of carrageenan include many brands of deli meats, soy milk, buttermilk, cottage cheese, cream, ice cream, yogurt, canned soups and broths, microwavable dinners, infant formulas and some dairy alternatives such as vegan cheeses, almond milk, nondairy creamers and nondairy desserts. Finding vegetarian or vegan foods without carrageenan is possible. Although it adds no nutritional value or flavor, carrageenan’s chemical structure makes it useful as a binder, thickening agent and stabilizer in a wide variety of foods and health care products such as toothpastes, cough medicines and bulk laxatives.

“Carrageenan is legally required to be listed among a product’s ingredients. Although the Food and Drug Administration still approves this ingredient, the National Organic Standards Board voted to remove carrageenan from their approved list in 2016. This means that foods made with carrageenan can no longer be labeled “USDA organic.” Choosing certified organic products and reading ingredient labels can ensure that the additive isn’t in the foods and products you buy.”

We were surprised to learn that that the common food additive carrageenan can trigger a reaction in people with AGS (Journal of Allergy and Clinical Immunology, December 2015).

— King Features