AllergyIntolerance

AllergyIntolerance refers to a range of conditions in which the immune system reacts to ordinarily harmless substances, or where adverse reactions occur without an immune basis. Allergies are immune-mediated, while intolerances are non-immunological or result from metabolic or enzymatic defects.

Most classic allergies are IgE-mediated, causing rapid onset symptoms such as hives, wheeze, vomiting, or anaphylaxis within minutes of exposure. Non-IgE mediated or mixed hypersensitivities can produce delayed or variable symptoms, involving cells other than IgE-bearing mast cells. Common clinical areas include allergic rhinitis, asthma, atopic dermatitis, and food, drug, and insect venom allergies.

Intolerances refer to adverse reactions not primarily immune. Lactose intolerance due to lactase deficiency is a common example; others include fructose intolerance and histamine intolerance. Some food reactions or chemical sensitivities have uncertain mechanisms and may not involve classic immune pathways.

Diagnosis rests on clinical history and test results. Skin prick tests and serum-specific IgE measurements support IgE-mediated disease, while patch testing assesses delayed-type contact allergies. Oral food challenges remain the gold standard for food allergies, particularly when test results are inconclusive. Elimination diets can aid diagnosis but should be supervised.

Management aims to avoid triggers and control symptoms. Treatments include antihistamines, intranasal or inhaled corticosteroids, bronchodilators, and, in anaphylaxis, epinephrine auto-injectors. Allergen immunotherapy can modify the disease course for certain allergies. Individuals with suspected severe reactions should carry an emergency plan and ensure access to care.