Why Do I Keep Getting Hives for No Reason?

Hives (also called urticaria) are itchy, red, and raised bumps on the skin. Hives can happen for several possible reasons, and they can also seem to appear without cause. Hives usually are not dangerous. They can be short term and disappear within a day, or they can last weeks or longer.

This article covers the types of hives and their causes, how to diagnose hives, how to treat and prevent hives, and when hives can be dangerous.

Types of Hives and Their Causes

There are a few types of hives, each with its own causes.

Acute Urticaria

"Acute urticaria" is the term for hives that last for less than six weeks. Possible causes for acute urticaria include:

• Allergies
• Food allergy reaction
• Drug reactions
• Viral infection
• Insect bites
• Pollen

Chronic Urticaria

Hives that last longer than six weeks are called chronic urticaria. Reasons behind chronic urticaria include:

• An autoimmune disorder (when the body's immune system, which fights off invaders like bacteria or injury, mistakenly attacks itself)
• Scratching or pressure on skin (like from tight clothing)
• Extreme heat or cold
• Sunlight
• Water or sweating
• Emotional stress

Chronic hives can last for years but often go away within one to two years.

Physical Urticaria

Physical urticaria is when hives are caused by the environment, including:

• Heat or cold
• Sunlight
• Plants
• Pressure on skin
• Contact with chemicals
• Vibrations

Dermatographism

"Dermatographism," meaning "skin writing," is when hives appear immediately after rubbing or scratching the skin.

Can Hives Be Caused by Nothing?

It is possible to break out in hives for an unknown reason. Hives that seem to be caused by nothing happen when there are no allergens or environmental conditions that could be possible triggers. At times, hives that seem to have no reason can be chronic.

Chronic Idiopathic Urticaria (CIU)

When hives last longer than six weeks without any apparent reason, a person might have chronic idiopathic urticaria (CIU). Antihistamines are the first-line treatment for CIU.

CIU is difficult to diagnose except by an allergist who takes a detailed history. CIU is not contagious or dangerous unless the hives occur with shortness of breath or other symptoms of anaphylaxis, which requires medical attention as soon as possible. CIU can go away on its own within one to five years.

Diagnosis 

Hives usually are diagnosed by an allergist or dermatologist examining the skin and getting a detailed medical history. Symptoms of hives include:

• Itching
• Swelling and redness
• Clear edges to skin bumps
• Bumpy skin joining together to cover large areas

For chronic hives, a healthcare provider may or may not recommend allergy testing, since environmental allergies are not usually a cause of hives. Diagnosis might also include reviewing the following:

• Other symptoms that occur with the hives
• How often the hives appear
• How the hives feel (itchy, painful, etc.)
• Where the hives appear
• If the hives leave any residual skin changes (discoloration, bruising)

Possible triggers also may be discussed, including:

• Foods (if allergies are causing the hives)
• Stress levels
• Medications
• Environment (bug bites, plants, etc.)
• Exposure to heat, cold, or sunlight
• If anything put pressure on your skin, including clothes or bags

Diagnosing CIU might include taking a blood test to test for how much histamine your body has. Histamine is a chemical that's released during an allergic reaction. High amounts of histamine in the blood may be a symptom of CIU if a patient's history is consistent with it.

Treatment

Ways to soothe the irritation caused by hives include:

• Stop scratching.
• Applying anti-itch cream
• Don't wear tight clothing that puts pressure on your skin.
• Avoid irritating chemicals and foods.
• Avoid extreme temperatures, including from sun or hot showers.

If hives require treatment, antihistamine medications are usually the first drug to try. They include but are not limited to:

• Benadryl (diphenhydramine)
• Zyrtec (cetirizine hydrochloride)
• Vistaril (hydroxyzine)
• Claritin (loratadine)

If chronic hives do not respond to antihistamines, they might be treated with an injection of an anti-allergy medication called Xolair (omalizumab). Xolair does come with a risk of side effects like body aches, nose bleeds, and nausea. The first dose of Xolair can include risk of severe allergic reaction for up to four days.

Delayed anaphylaxis has been reported but is very rare. Treatment will not cure hives but only make symptoms more manageable until the hives clear up on their own.

Prevention

Hives can be prevented by:

• Avoiding allergic triggers, like certain foods or chemicals
• Wearing loose clothing
• Avoiding extreme temperatures or sunlight
• Keeping the skin dry, especially after exercise
• Monitoring reactions to medication
• Managing emotional stress
• Following your healthcare provider's treatment plan
  

Summary

Hives are red, itchy welts on the skin that can be caused by an allergic reaction, a viral infection, insect bites, extreme heat or cold, sweating, emotional stress, or a serious disease (in rare cases). Sometimes, hives appear for no apparent reason. Hives usually go away on their own, but treatment can include avoiding skin irritants like extreme temperatures, tight clothes, and triggering foods and chemicals. Antihistamines can be used to treat hives.

A Word From Verywell

Hives can be difficult to live with, especially when they seem to appear for no apparent reason. But it's important to remember you're not alone. Most hives do go away on their own, sometimes in a matter of hours to days.

If your hives are chronic, it might help to note when they occur and what may have caused them so you can avoid these triggers in the future. You may also want to take an antihistamine under the guidance of a medical professional like an allergist. If your hives don't seem to respond to medications and waiting for them to disappear causes undue stress, consider finding support from others living with difficult skin conditions.