Hives vs Rash - What's the difference between them?
Medically reviewed by C. Fookes, BPharm. Last updated on July 29, 2019.
The main difference between hives and a rash is that hives are a particular type of rash, characterized by swollen, pale-red or skin-colored bumps on the skin that appear and disappear quickly, and tend to “blanch” (which means turn white) when pressed. Hives are also known as urticaria.
Hives are a type of rash, but there are many other different ways rashes present. Both hives and rashes tend to be itchy.
What are hives?
Hives are an outbreak of swollen, pale red bumps that appear suddenly on the skin. These bumps are sometimes called wheals or welts, and they may be circular or irregular in shape and range in size from pin-size dots to large map-like patches.
They can appear anywhere on the body, including the face, lips, tongue, throat, or ears. Their edges are distinct, and the area of skin affected by the hive is smooth and elevated above the surrounding area of skin (reflecting the fluid collected in the layer of skin below the surface).
Angioedema is similar to hives, but the swelling occurs deeper within the skin instead of on the surface, so the swelling is more noticeable and worrying. Occasionally, angioedema can be life-threatening, because the swelling can occur around the throat, tongue or lungs and restrict breathing. Other common areas affected by angioedema include the eyes, lips and sometimes the genitals, hands, or feet. See your doctor as soon as possible if you develop angioedema.
Some wheals may look different from others, for example, some may be red, whereas others may be pale; some may be rounded, whereas others may be flat on top. Hives are usually incredibly itchy and they characteristically change in size and shape and may join together to form larger areas known as plaques. Sometimes they disappear for a few hours only to reappear in a different formation later.
Most people think hives are caused by an allergy, but in fact, most cases of hives occur for non-allergic reasons, although allergies are a common cause. Other causes of hives include:
- Blood transfusions
- Certain foods: The most common foods implicated are nuts, chocolate, fish, tomatoes, eggs, fresh berries, and milk. Fresh foods cause hives more often than cooked foods
- Chemicals in certain foods (such as additives and preservatives)
- Infections (eg, colds, infectious mononucleosis, hepatitis, urinary tract infections, and strep throat)
- Insect bites or stings
- Medications (such as aspirin, NSAIDs [eg, ibuprofen], ACE inhibitors, codeine, sulfa drugs)
- Physical stimuli, such as pressure, cold, heat, exercise or sun exposure
- An underlying internal disease (such as thyroid disease, cancer, or hepatitis).
Hives (urticaria) are usually classified as acute (lasting less than six weeks) or chronic (lasting more than six weeks). Some cases are mild, while others are severe. Scratching, alcoholic beverages, exercise, and stress may worsen hives.
The most frequently recommended treatment for hives is antihistamines. These work by blocking the effect of histamine, which is a chemical in the skin that can cause inflammation, swelling, and itching. Cold compresses or anti-itch salves may also help ease symptoms.
What is a rash?
A rash is an irritated area of skin. Most rashes are characterized by small bumps of skin, are itchy and look red. Sometimes the skin may be broken from scratching. In some types of rashes, blisters may form.
Rashes may be a symptom of an underlying medical problem and some people are more likely than others to develop rashes. Other common causes of rashes include:
- Chemical exposure
- Insects, spiders, or jellyfish
- Irritating substances
- Medications (eg, amoxicillin, sulfa drugs)
- Plants (eg, poison ivy)
Some rashes develop suddenly, whereas others form over several days. Treatments vary, depending on what caused the rash in the first place but may include moisturizers, lotions, corticosteroids creams (which relieve redness and swelling) and antihistamines (which relieve redness and itching).
If your rash doesn’t go away within a few days, you have other worrying symptoms, or is very severe, see your health care provider.
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