A Guide to Allergic Reactions, Bites, and Treatments

Seasonal allergies plague millions when trees, grasses, and weeds release pollen. Spring brings tree pollen, summer features grass pollen, and fall means ragweed and other weed pollen. Weather affects pollen counts—dry, windy days spread more pollen while rain temporarily clears the air.

Year-round allergens lurk indoors. Dust mites thrive in bedding, carpets, and upholstered furniture. Pet dander from cats, dogs, and other animals triggers reactions even in homes without pets, as dander travels on clothing. Mold grows in damp areas like bathrooms, basements, and leaky windows. Cockroach droppings in urban areas are significant asthma triggers.

True food allergies involve immune system reactions and can be life-threatening. The “Big 9” allergens cause most food allergic reactions: milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, soy, and sesame. These allergies can cause immediate reactions ranging from hives to anaphylaxis.

Food intolerances don’t involve the immune system but cause uncomfortable symptoms. Lactose intolerance causes digestive upset from the inability to digest milk sugar. Gluten sensitivity causes various symptoms without the immune response seen in celiac disease. These conditions are uncomfortable but not life-threatening, like true allergies.

Drug allergies can develop even to medications you’ve taken before without problems. Antibiotics, especially penicillin and sulfa drugs, commonly cause allergic reactions. Aspirin and NSAIDs trigger reactions in some people, particularly those with asthma. Contrast dyes used in imaging tests can cause reactions ranging from mild itching to severe anaphylaxis.

Local anesthetics, opioid pain medications, and even seemingly harmless drugs like vitamins can trigger allergic responses. Always inform healthcare providers about past medication reactions, even if they seemed minor.

Stinging insects inject venom that causes normal pain and swelling, but some people develop dangerous allergies. Honeybees leave their stinger behind and die, while wasps, yellow jackets, and hornets can sting repeatedly. Fire ants bite to hold on, then sting from their abdomen, creating characteristic pustules.

Cross-reactivity exists between different stinging insects, so allergy to one might mean reactions to others. Interestingly, mosquito bites rarely cause true allergic reactions despite being annoying. The large, itchy welts some people develop are usually just normal responses.

Poison ivy, poison oak, and poison sumac contain urushiol oil, which causes allergic contact dermatitis in most people. The oil easily transfers from plants to skin, clothing, tools, and pet fur. Reactions typically appear 12-48 hours after contact and can last weeks. Contrary to myth, the fluid from blisters doesn’t spread the rash, but urushiol oil on hands or under fingernails can.

Common contact allergens may include nickel in jewelry and clothing fasteners, latex in gloves and medical equipment, fragrances in cosmetics and cleaners, and preservatives in personal care products. Patch testing can identify specific contact allergies.

Exercise-induced anaphylaxis is rare but serious. Some people only react when exercising after eating specific foods. Physical urticaria causes hives from pressure, cold, heat, or vibration. Cold urticaria creates hives and swelling from cold exposure, potentially life-threatening when swimming in cold water.

Cholinergic urticaria causes tiny hives from increased body temperature during exercise, hot showers, or emotional stress. These physical triggers can be challenging to avoid, but understanding them helps with management.