According to the National Institutes of Health (NIH), allergies are exaggerated immune system responses to substances (allergens) that are generally not harmful. People with overly sensitive immune systems develop a number of symptoms (rash, hives, nasal congestion, itching, runny nose, breathing problems, headache) in response to various allergens. A number of common allergies affect humans.
Food Allergies
Food allergies are common in both children and adults. According to Medical News Today, the eight most common foods to which people are allergic are milk, eggs, peanuts (groundnuts), nuts from trees (including almonds, walnuts, Brazil nuts and hazelnuts), fish, shellfish (mussels, crab and shrimp), soy and wheat. These foods are responsible for 90 percent of all food allergies. The most common allergies among children are to eggs, milk and peanuts. Most outgrow these allergies in early childhood. The most common food allergies among adults are tree nuts, peanuts, fish, eggs and shellfish.
Hay Fever
According to the Mayo Clinic, hay fever (or allergic rhinitis) is a condition caused by an allergic reaction to airborne allergens. For some people, hay fever symptoms may be minor or seasonal; for others, symptoms may be severe or occur year-round.
A common seasonal airborne allergen is pollen. Tree pollen (spring), grass pollen (late spring and summer) and weed pollen (fall) are released into the air, commonly causing seasonal allergic responses.
Mold (a type of fungus) is an airborne allergen that reproduces by releasing spores into the air. According to the Asthma and Allergy Foundation of America, a few dozen types of molds cause allergic reactions in humans. These include outdoor molds (those growing on rotting logs or leaves) and indoor molds (those growing in damp places such as basements, kitchens and bathrooms). Although some outdoor molds commonly cause allergies in the mid to late summer months, other indoor molds can cause allergies year-round.
Pet dander is a common airborne allergen that may cause allergies year-round. Proteins found in the skin flakes and saliva of furry pets such as cats and dogs may cause the body's immune system to react.
According to the Mayo Clinic, other year-round hay fever allergens include cockroaches and dust mites. Dust mites are microscopic bugs that thrive in warm, humid environments and are found in bedding, furniture and carpets. Dust mite proteins can cause an immune response in some people.
Other Common Allergies
There are a number of other common allergies. Medications may cause allergic reactions. According to the NIH, penicillin and other antibiotics are the most common causes of drug allergies. Other common allergy-causing drugs include sulfa drugs (sulfonamides), anticonvulsants, insulin preparations and x-ray contrast drugs that contain iodine.
Chemicals and fragrances (perfumes, soaps and detergents, cosmetics) can irritate the skin and nasal passages and prompt allergic reactions, as can insect stings (bees, wasps).
According to Family Doctor, latex allergies are also common. Latex is processed rubber latex used in things such as balloons, dishwashing gloves, baby bottle nipples and pacifiers and rubber bands. Proteins in the rubber can cause allergic reactions in some people.
