Seaweed is a popular addition to many diets and products due to its nutritional content. Found in various cuisines, it is increasingly present in processed foods, supplements, and cosmetics. Like any food, seaweed contains proteins that can trigger allergic reactions in some individuals.
How Seaweed Allergies Develop
A true food allergy occurs when the immune system mistakenly identifies specific proteins in a food as harmful. With seaweed, the immune system produces immunoglobulin E (IgE) antibodies against these proteins. Subsequent exposure triggers a rapid immune response, releasing chemicals like histamine, which cause allergic symptoms.
Allergenic proteins in seaweed include phycobiliproteins and phycolectins, found in red seaweed species like Porphyra (nori) and Chondrus crispus. Brown seaweeds may contain proteins similar to crustacean allergens, potentially causing cross-reactivity for those with shellfish allergies. A true IgE-mediated allergy differs from other adverse reactions, such as sensitivity to high iodine content. While iodine sensitivity can cause symptoms, it does not involve the same immune pathway.
Recognizing Allergic Reactions
Symptoms of a seaweed allergy can range from mild to severe and typically appear shortly after contact or consumption. Skin reactions may include itching, hives, eczema, or a rash.
Digestive issues are common, including nausea, vomiting, abdominal pain, or diarrhea. Respiratory symptoms like wheezing, shortness of breath, or nasal congestion can also occur. The most severe reaction, anaphylaxis, can affect multiple body systems and may involve a rapid pulse, dizziness, or fainting, requiring immediate medical intervention.
Diagnosis and Living with a Seaweed Allergy
Diagnosing a seaweed allergy starts with a consultation with an allergist or immunologist. Diagnostic tests include a skin prick test, where seaweed extract is applied to the skin, or blood tests measuring specific IgE antibodies to seaweed proteins. An oral food challenge, conducted under medical supervision, may also confirm the allergy.
Management of a diagnosed seaweed allergy involves strict avoidance of seaweed and its products. Careful reading of food labels is essential, as seaweed-derived ingredients are used in many processed foods, supplements, and cosmetics. Common forms and extracts include nori, kombu, wakame, dulse, agar-agar (E406), and carrageenan (E407). Carrageenan, a widely used food additive from red seaweed, functions as a thickener and stabilizer in items like dairy products and deli meats. For mild reactions, antihistamines can alleviate symptoms, while individuals at risk of anaphylaxis should carry an epinephrine auto-injector for emergency treatment.