An allergy is the body's defensive response to a substance that it has deemed a threat. In the case of allergies, the substance is usually something relatively benign, which the body has misinterpreted to be harmful. As a result, those with allergic sensitivities can experience unpleasant symptoms from exposure to objects and substances that cause no negative effects in most of the population. Sometimes these allergic sensitivities manifest in the form of skin rashes.
Allergen Consumption
Various foods, beverages and medications can cause allergic skin reactions in those who have been sensitized to that particular substance. The Asthma and Allergy Foundation of America reports that 1 to 2 percent of all children and adults have true food allergies, while 3 to 8 percent of children experience reactions to some foods rather than true allergies.
The symptoms of these allergies can occur within minutes, but may take up to 2 hours after the allergen has been consumed. Allergies to nuts, fish and eggs are the most common serious reactions.
Medline Plus, a website of the National Institutes of Health, states that minor skin rashes are prevalent in most allergic reactions to drugs. Antibiotics such as penicillin are the drugs that most frequently cause allergic reactions. Sulfa drugs, anticonvulsants, insulin and X-ray dyes that contain iodine also commonly cause allergies.
Skin-related symptoms such as swelling, itchiness and hives can precede even more serious symptoms. Anaphylaxis, a condition wherein the blood pressure falls, the throat constricts and the individual experiences difficulty breathing, can be fatal.
Skin Contact
Allergic contact dermatitis occurs when the skin comes in direct contact with an allergen. Poison ivy is the most common example of an allergen which causes allergic contact dermatitis. This type of skin rash is characterized by itchy, swollen, inflamed skin, sometimes accompanied by bumps and blisters.
EczemaNet states that more than 3,000 known allergens have been observed to cause contact dermatitis. Rubber is often the culprit. Allergic skin rashes caused by the elastic in underwear, or the rubber in shoes, have been reported. Metals such as nickel, which is used in jewelry, buttons and zippers, have also caused the rash associated with contact dermatitis. Cosmetics often cause allergic skin reactions, most often due to the fragrances listed in their ingredients.
Allergen Inhalation
Airborne allergens can also be absorbed though the lungs, causing reactions that include skin rashes such as hives. Hay fever is a common example of this type of allergic reaction. It's extremely difficult to avoid inhaling the various pollens that waft through the air during the spring, summer and fall. Ragweed is the main cause of hay fever, but other weeds, grasses and trees can also cause allergic reactions, according to the University of Maryland Medical Center.
Mold, which grows in moist places such as damp basements, bathrooms and air conditioners, can be inhaled causing an allergic response. Dust mites and animal dander are other airborne allergens that frequently plague those with allergic sensitivities.
