•Foods (commonly eggs, shellfish, nuts, berries, dyes, or other additives)
•Drugs (any drug can touch off an allergic reaction, although allergies to penicillin
, sulfa, and
aspirin are especially common)
plants (nettles, poison ivy, poison oak, and so on)
•Insect bites or stings
•Exposure to heat, cold, or sunshine
Comfort is the main goal of treatment, since most hive outbreaks are relatively minor and short-lived.