Hives are a type of rash that causes itchy welts on the skin. People can tell them apart from other rashes, like heat rash, by their smooth, raised appearance.
Unlike other rashes, hives generally do not come with dryness, peeling, or flaking. They also do not typically leave lasting marks on the skin.
Hives are not dangerous in themselves, but sometimes, they are the first sign of a severe allergic reaction known as anaphylaxis. A person should call emergency services immediately if someone develops swelling in the mouth and airways, wheezing, or difficulty breathing.
Read on to learn more about the differences between hives versus other rashes.
Hives are a type of rash with a distinctive appearance, causing raised, flat welts on the skin. The welts will usually appear quickly, either in one specific area or across a larger part of the body.
In lighter skin tones, hives are often red. In darker skin tones, they may be red, purple, or a similar color to the rest of the skin. Other characteristics of hives include:
- a bumpy, but not blistered, texture
- blanching, which means the center of the hive loses its color when a person presses it
There are many types of rash, and some have similar symptoms to hives. Here are some examples.
There are several types of dermatitis, including atopic dermatitis and contact dermatitis. Atopic dermatitis is a chronic condition that often appears in childhood and can last for any length of time. It may come and go over a person’s lifetime.
Similarly to hives, contact dermatitis occurs upon exposure to an allergen or irritant, such as poison ivy. It can also look similar to hives. However, contact dermatitis often lasts longer and may take 14–28 days to resolve. This condition also causes bumps that are more like blisters and may be more painful than itchy.
The rash itself consists of blocked sweat ducts in the skin, which causes tiny bumps. Heat rash only affects the area where the sweat ducts are blocked — it will not spread.
Many insect bites get better on their own. However, people should seek medical care if the swelling spreads, has visible streaks, or becomes very painful.
People can be allergic to some insect bites. This may cause hives in addition to the bite itself. This is not necessarily a cause for concern, but less commonly, it can be an early sign of anaphylaxis.
Cellulitis is a skin infection in the deeper layers of the skin. It can become serious if it spreads. The symptoms include:
- an inflamed, swollen area of the skin
- tenderness to the touch
- noticeable warmth
- swollen glands
The infection can begin if bacteria get into the skin due to an injury or another type of rash. For example, it may occur as a complication of an insect bite, cut, or broken skin due to eczema.
Cellulitis requires treatment with antibiotics.
A rash may be hives rather than another type of rash if the welts:
- appear shortly after exposure to a trigger
- affect a well-defined area of the skin, although this area may change shape or move around
- do not cause blistering, flaking, or broken skin
- change color when a person presses them or rolls a glass against the skin
- are itchy — although many rashes cause itchiness, not all do
In many cases, hives occur due to an allergic reaction. A person may have an allergy to:
- specific foods
- insect bites or stings
- pet dander
- pollen or plants
People can also experience physical hives, which is when pressure, heat, or cold trigger hives. Triggers may include:
- constrictive clothing
- changes in temperature
- being too hot
- sun exposure
Sometimes, people develop chronic hives, which persist for at least 6 weeks. Chronic hives may occur alongside an autoimmune disorder, but often, the cause is unclear. It usually gets better on its own over time, but this can take years. On average, the condition lasts
Acute or short-term hives usually resolve within 24 hours, with or without treatment. People may find it helpful to apply a cool compress to ease itchiness or to take an antihistamine if they have allergies.
Treatment for chronic hives aims to manage symptoms and avoid triggers. A doctor
A person should speak with a doctor about any unusual or persistent rash that appears without a known cause. Other conditions can look similar to hives and may require treatment.
People should also contact a doctor promptly if a person experiences:
- persistent hives that keep returning
- a rash that is painful or bleeds
- symptoms of infection, such as swollen skin, pus, fever, or feeling generally unwell
A person should call 911 or the number of the nearest emergency department if someone develops:
- a rash that starts suddenly, spreads rapidly, or covers a large area of the body
- a rash following a bite or sting, along with severe pain, twitching, tingling, numbness, or other concerning symptoms
- a rash that does not disappear under a glass, particularly if the person also has:
People should call 911 if someone has any symptoms that could indicate anaphylaxis, such as difficulty breathing. People should also seek emergency care if they come into contact with an allergen that previously led to anaphylaxis.
Anaphylaxis: Symptoms and what to do
Anaphylaxis is a severe allergic reaction that can be life threatening. The symptoms develop suddenly and include:
- swelling of the face or mouth
- fast, shallow breathing
- a fast heart rate
- clammy skin
- anxiety or confusion
- blue or white lips
- fainting or loss of consciousness
If someone has these symptoms:
- Check whether they are carrying an epinephrine pen. If they are, follow the instructions on the side of the pen to use it.
- Dial 911 or the number of the nearest emergency department.
- Lay the person down from a standing position. If they have vomited, turn them onto their side.
- Stay with them until the emergency services arrive.
Some people may need more than one epinephrine injection. If the symptoms do not improve in 5–15 minutes, or they come back, use a second pen if the person has one.
Hives can look and behave differently than other types of rash. They cause flat, raised welts on the skin that can appear and disappear quickly. Unlike other rashes, hives are typically smooth and do not cause dryness, peeling, or flaking.
If a person is unsure what is causing their rash, they should seek advice from a medical professional. Trying to self-diagnose is risky and may mean a person does not get the treatment they need.
People who frequently develop hives, a rash that does not go away, or other concerning symptoms should contact a doctor.