There are specific characteristics that help you identify hives. For instance, they often have well-defined borders. Hives also tend to cause itching and discomfort that’s worse at night.
Hives are a specific type of rash caused when tissues beneath the surface of the skin fill with fluid, causing raised, red, itchy bumps referred to as weals (or welts). Allergy is the most common cause, but hives can also occur due to an infection, autoimmune disease, or sudden changes in the environment.
The article details the signs and symptoms of hives so that you can tell them from other types of rashes. It also explains how hives can differ based on the underlying cause and what each specific skin reaction looks like.
Frequent Symptoms
Urticaria is most often caused by an allergy or infection, but it can occur due to stress, vibration, or sudden changes in the environment. An abnormal immune response causes blood vessels to leak fluid into the middle layer of skin, called the dermis. Hives are the result.
You can tell hives from other types of rashes by the following signs and symptoms:
Hives cause raised, red, welt-like bumps. Hives usually have well-defined borders. Hives cause itching, sometimes intense and often worse at night. Hives can sometimes cause burning or stinging. Hives blanch (whiten) when pressed. When hives resolve, they leave no scarring or tissue damage.
Hive can appear on any part of the body and be as small as a pinpoint or large as a plate. They can change shape, move around, meld, disappear, and reappear over short periods of time.
Hives most often appear in the evening or early morning just after waking. They generally aren’t associated with fever, nausea, muscle aches, joint pain, or headaches unless an infection is involved.
Acute vs. Chronic
Urticaria affects up to 20% of people of all ages, races, and genders. Hives can either be acute or chronic depending on how long they last. Acute hives last for less than six weeks, while chronic hives persist beyond six weeks.
Acute urticaria is more common in children and young adults. The majority are idiopathic, meaning that the cause is unknown. Acute hives tend to start and stop quickly, often lasting a few hours and rarely for more than a few days. If a cause is found, it is most often an infection, insect bite, or a drug or food allergy.
Chronic urticaria is often idiopathic and can recur over the course of months or years. In one 2013 study, 70% of people with chronic hives had symptoms that lasted for more than a year, while 14% had symptoms for five or more years. In half of the cases, no cause was found.
Symptoms by Type
The look and location of hives can vary based on the cause. The appearance can sometimes give a clue as to the cause but not always.
Examples include:
Cold urticaria: This is caused by exposure to cold temperatures. It usually causes welts between a quarter of an inch to one inch in size, either slightly reddish or skin-colored. Fainting can occur if large areas of skin are involved. Cholinergic urticaria: Also known as heat rash, this type of hive is caused by excessive sweating, usually due to strenuous exercise. It causes very small weals surrounded by bright red flares. Dermographism urticaria: This is caused by the firm stroking or scratching of the skin, creating hives along the line of contact. The weals tend to appear within five to 10 minutes and disappear within 10 to 15 minutes. Pressure urticaria: This type is caused when pressure is placed on the skin, such as when you wear tight clothing or stand on your feet for too long. It causes dense, red, itchy weals that can sometimes be a little painful. Solar urticaria: Exposure to ultraviolet (UV) light from the sun can cause hives on sun-exposed areas of skin, often within minutes. The hives will appear “angry,” often with intense redness and warmth. Fainting can occur if the hives are widespread. Stress urticaria: This is a type of chronic hives caused by emotional stress. With that said, the condition is hard to define as stress is only presumed to be the cause. The weals tend to be larger and can occur on any part of the body. Vibratory urticaria: Vibrations, such as clapping or a bumpy car ride, can cause hives in some people. The hives tend to come and go within an hour. Flushing, headaches, blurry vision, or a metallic taste can sometimes occur along with them. Water urticaria: This rare form of hives is caused by contact with water. The hives are usually small and are most often on the neck, upper trunk, and arms. They also tend to come and go within an hour.
Rare Symptoms
Rarely, urticaria can progress to a severe, all-body allergy known as anaphylaxis. Anaphylaxis affects many organ systems at once and can be life-threatening if not treated as an emergency. Hives are one of the possible features of anaphylaxis and will typically be severe.
Symptoms of anaphylaxis include:
Widespread hives or rash Shortness of breath Wheezing Dizziness or lightheadedness Stomach cramps Nausea or vomiting Diarrhea Rapid or irregular heartbeat Swelling of the lips, tongue, or throat Confusion A feeling of impending doom Fainting Seizures
If left untreated, anaphylaxis can lead to shock, coma, asphyxiation, cardiac arrest, and death.
When to See a Doctor
If you have hives that are not severe and only cause mild itching, you can usually treat them at home. Most cases will resolve within a few hours to several days. If they last for more than a week or worsen, see a doctor as soon as possible.
If symptoms are recurrent, ask your doctor for a referral to either a dermatologist, who specializes in diseases of the skin, or an allergist, who specializes in allergies.
Based on your symptoms and medical history, your doctor may also want to check for infections such as hepatitis B or autoimmune disorders like Hashimoto’s disease, in which hives are common.
Summary
Urticaria (hives) is caused by an abnormal immune response in which fluids leak into tissues beneath the surface of the skin, causing them to swell. Symptoms include a raised, red, itchy, welt-like rash with well-defined borders.
There was an error. Please try again.
Allergies and infections are common causes, but urticaria can also be triggered by cold, heat, pressure, vibration, stress, and even water. The location, timing, and look of the rash can provide clues as to what is causing it.
Some cases have no known cause, especially with chronic hives, which can persist or recur for months and even years.
Airborne allergensApplying direct pressure to the skin (such as wearing tight clothing)Contact allergensDrug hypersensitivityEnvironmental changes (like changes in temperature, excessive sun exposure, or extreme vibrations)ExerciseFood allergiesInsect bitesStress
Some medical conditions, including HIV and hepatitis, can also make you more prone to hives.
