Can allergies cause hives?

How allergies cause it

Hives are itchy, red or white bumps, welts or patches on the skin, and they are common: nearly one in four people have had them.¹

Allergic reactions cause the body to release chemicals that can make the skin swell up in hives.³ Hives may appear on different parts of the body but usually last 24 hours or less.⁷ They usually appear and disappear suddenly and may come back over short periods of time.²

ACAAI says acute urticaria, hives that last no more than six weeks, is most commonly caused by exposure to an allergen or by an infection.⁶ AAFA lists food allergies, pet dander, pollen, insect stings or bites, latex and some drugs among the triggers.² ACAAI’s examples of common food triggers are peanuts, eggs, nuts, milk and shellfish.⁷ A food reaction usually starts within a few minutes to two hours of eating, and many reactions start with skin symptoms such as hives.⁸

Angioedema, a swelling of the deeper layers of the skin, commonly occurs with hives. It often involves the eyelids, lips, tongue, hands or feet.⁵ In rare cases, hives can cause a dangerous swelling in the airways that makes it hard to breathe, which is a medical emergency.³ Hives can also be a symptom of anaphylaxis, a life-threatening allergic reaction, though this is rare.¹

Allergies or something else?

Many hives have nothing to do with allergies. AAFA lists physical stimuli such as pressure, cold, heat, vibration, exercise or sun exposure, bacterial infections such as urinary tract infections and strep throat, and viral infections such as the common cold.² AAAAI adds stress and exposure to certain chemicals, and says one of the most common causes of acute hives in children is a viral infection.¹

Timing offers a few clues. Acute hives sometimes appear after eating a particular food or coming in contact with a particular trigger.⁴ They can last less than a day, or up to six weeks.¹

Hives that last more than six weeks are called chronic hives.⁶ These are rarely allergic: only a small percentage of chronic hives are due to an allergy.¹ ACAAI says the cause of chronic urticaria is largely unknown.⁶

Whatever the cause, hives are not contagious.²

When to see a doctor

Call 911 if you have hives along with fainting, shortness of breath, tightness in your throat, tongue or face swelling, or wheezing.¹ AAFA also says to go to the emergency room or call 911 if your hives are severe and cover a large area of your body.² If hives leave bruises, AAAAI says it is important for a doctor to rule out other causes.⁴

An allergist can examine you and do testing to help determine the cause of a skin reaction.⁶ Chronic hives are rarely caused by specific triggers, so allergy tests are usually not helpful for them.⁴