Dryer sheets help to cut down on static in your laundry. They can also trigger allergic reactions in some people, usually characterized by a skin reaction known as contact dermatitis.
Symptoms of an allergic reaction to dryer sheets include reddened skin, itchy hives, and swollen skin around the rash. The reaction usually occurs on skin that has come in direct contact with clothing treated with a dryer sheet.
Dryer sheet allergies are triggered by chemical anti-static agents within the sheet. The perfume that scents the sheet can also cause an allergic reaction, according to "Essential Pediatric Allergy, Asthma and Immunology."
In the long term, the best treatment for dryer sheet allergy is not to use the sheets that cause the reaction. In the short term, taking an antihistamine can relieve skin itching and hives.