Plant Allergies: Latex, Carrageenans

One in four or five Americans suffer from a misguided immunologic reaction against inoffensive substances -- allergens -- such as pollens, animal danders, foods, cigarette smoke, industrial fumes, insects and their venoms, and medications. Because these allergens stimulate the immune system at different body sites, they give rise to an enormous variety of symptoms. Allergens in the upper airways cause sneezing and nasal congestion (allergic rhinitis, including hay fever); allergens in the lower airways cause bronchoconstriction and wheezing (asthma); food allergens cause nausea, vomiting, abdominal cramps, and diarrhea; topical allergens cause contact dermatitis.

The most serious form of allergic reaction -- anaphylaxis -- occurs when an allergen enters the circulation and causes an acute, explosive release of mediators from mast cells, resulting in serious symptoms within minutes of allergen exposure. Severe anaphylaxis is a medical emergency; prompt attention is necessary to prevent death from shock or suffocation (caused by swelling of the vocal cords). Pruritus, urticaria, and bronchoconstriction are common allergic reactions, and some patients have gastrointestinal symptoms. In some cases, anaphylactic symptoms are preceded by an aura, and patients who experience recurrent anaphylaxis report that the same constellation of symptoms accompanies each attack. Treatment usually is administered as an injection of epinephrine to inhibit mediator release, open airways, and block vasodilation.

Plants are the most common source of allergens, with pollens and foods (especially tomatoes, onion, garlic, peanuts, and various fruits) heading the list. Approximately 15% of Americans have pollen sensitivity (hay fever), and many of these also have food allergies. For example, people with grass pollen allergy often cross-react to certain foods. Allergies are treated with antihistamines or, when these agents are ineffective, with inhaled corticosteroids. Severe cases are treated with immunotherapy (injection with increasing doses of the allergen). These "allergy shots" can be helpful, although protection is rarely complete. Sometimes pollen immunotherapy can reduce food hypersensitivity in children.

One common and often overlooked plant allergen is latex, an emulsion of rubber globules from the milky sap of Euphorbiaceae plants. The allergy develops when latex protein fragments come into contact with the skin or mucosa, causing contact dermatitis, pruritus, urticaria, conjunctivitis, rhinitis, asthma, and even anaphylaxis. Individuals at increased risk include latex industry workers, health-care personnel who wear latex gloves, patients who undergo frequent surgeries, atopic individuals (who have a general predisposition to allergic reactions), and, in particular, individuals with neural tube defects. Again, cross reactions are common; people with latex allergy often report allergies to avocados, chestnuts, bananas, and other fresh fruits. In some cases, latex-sensitive patients become anaphylactically allergic to fresh fruits; in other cases, the fruit allergy shows up first, followed by latex allergy on exposure to latex. Diagnosing latex allergy requires the utmost care. One patient who tested positive for multiple allergens on skin prick turned out to have latex allergy; the health-care worker who administered the skin-prick test was wearing latex gloves.

Carrageenan allergy is another difficult-to-detect plant allergy. Carrageenans are gelatinous substances obtained originally from seaweed (Irish moss), and now from several marine algae. They are commonly used as emulsifying, suspending, and clarifying agents in manufactured foods (certain dairy products, dressings, sauces), beverages, pharmaceuticals, cosmetics, and polishes. One patient undergoing a diagnostic barium procedure for gastrointestinal symptoms had an anaphylactic reaction to the barium enema solution. At first, the latex in the enema device was suspected, but the patient did not test positive to latex. Instead, she tested positive for the carrageenan used as an emulsifying agent in the barium suspension.
Ref:Tomazic VJ et al. J Allergy Clin Immunol.