What Causes Hives? Everything You Need To Know

August 26, 2025 6:16 pm

Hives are those sudden, itchy, raised patches or welts that can appear anywhere on the skin. They might be small and round, large and uneven, or even join together to form bigger swollen areas. Hives can come on quickly and sometimes disappear just as fast, leaving many people wondering what causes them in the first place.

If you have ever woken up with mysterious red marks or felt your skin start to itch after eating, exercising, or being outside, you are not alone. Hives are surprisingly common, and while they can be alarming, most cases are harmless and temporary. Still, knowing the possible causes can help you understand what is happening to your body and how to prevent it from happening again.

This guide will cover everything you might want to know about what causes hives, how they develop, and what you can do about them.

 

What Are Hives?

Hives, also called urticaria, are a skin reaction where red or skin-colored welts appear on the surface. They can be as small as a pinhead or as large as a dinner plate. The welts may feel warm, itchy, or slightly painful, and they often change shape or location within hours.

Hives occur when your body releases histamine and other chemicals from special immune cells called mast cells. This chemical release causes fluid to leak from tiny blood vessels under the skin, leading to swelling and redness.

Some hives disappear within minutes or hours, while others linger for days or even weeks. The duration and frequency often depend on the underlying cause.

 

The Different Types of Hives

Before we look at the causes, it helps to understand that not all hives are the same.

• Acute hives: These last less than six weeks and are often linked to allergies, infections, or environmental triggers.

• Chronic hives: These last longer than six weeks and may have less obvious causes. They often come and go unpredictably.

• Physical hives: These are triggered by direct physical factors such as pressure, temperature changes, or sunlight.

 

What Causes Hives? The Most Common Triggers

The truth is that hives can have many possible causes. Sometimes the trigger is easy to spot, like eating a certain food or taking a specific medication. Other times, the cause can be much harder to identify. Here are the main categories of triggers.

1. Allergic Reactions

Allergic reactions are one of the most common causes of hives. When your body detects something it sees as harmful, even if it is harmless to most people, your immune system releases histamine to fight it off. This release often causes hives to appear.

Common allergy-related triggers include –

• Foods such as nuts, shellfish, eggs, milk, or wheat
• Medications like antibiotics, aspirin, or ibuprofen
• Insect stings or bites
• Latex or certain chemicals

If hives appear within minutes or hours of exposure to one of these triggers, an allergy could be the cause. In severe cases, an allergic reaction can lead to anaphylaxis, which requires immediate medical attention.

2. Infections

Infections are another frequent cause, especially in children. The body’s immune system reacts to fight off the infection, and hives can be part of this response.

Infections that may cause hives include –

• Viral infections like the common cold or flu
• Strep throat
• Urinary tract infections
• Hepatitis and other viral illnesses

In these situations, the hives usually fade once the infection is gone.

3. Environmental Triggers

Your surroundings can sometimes trigger hives. Factors such as temperature changes, sunlight, or direct skin contact with irritants can cause the reaction.

Environmental triggers include –

• Cold air or cold water
• Heat or hot showers
• Sunlight exposure
• Pressure from tight clothing or straps
• Contact with certain plants or chemicals

Some people also have a condition called dermatographism, where even light scratching can cause hives along the scratched area.

4. Stress

Stress does not directly cause hives, but it can make the body more sensitive to other triggers. If you are prone to hives, you might notice flare-ups during times of emotional or physical stress.

5. Physical Activity

Exercise can sometimes lead to a specific type of hives called cholinergic urticaria. This condition is triggered by an increase in body temperature from activities like working out, taking a hot shower, or eating spicy foods. Small, itchy bumps appear and may last from a few minutes to an hour.

6. Underlying Health Conditions

Chronic hives can sometimes be linked to other medical conditions. These may include:

• Autoimmune diseases such as lupus or thyroid disorders
• Hormonal imbalances
• Liver or kidney problems

While rare, certain cancers can also cause hives as part of the body’s immune response.

7. Unknown Causes

Sometimes, even after thorough testing, the cause remains unknown. This is called idiopathic urticaria. The good news is that many people with idiopathic hives still respond well to treatment, even without identifying the trigger.

 

How Hives Develop in the Body

When the immune system detects what it thinks is a threat, mast cells in the skin release histamine. This chemical widens tiny blood vessels and allows fluid to leak into the surrounding tissue. The result is the swelling, redness, and itching we see in hives.

The reaction can occur within minutes of exposure to a trigger, but in some cases, it might take hours. Hives can appear in one place and then fade and reappear in another part of the body.

 

Symptoms That Accompany Hives

In addition to raised, itchy welts, hives can sometimes cause:

• Burning or stinging sensations
• Swelling of the lips, eyelids, or inside the mouth (angioedema)
• Redness or warmth in affected areas

If you ever experience swelling in your throat or difficulty breathing along with hives, it is important to seek emergency medical care immediately.

 

When to See a Doctor

Most hives go away on their own within 24 hours. However, you should see a healthcare provider if:

• Hives last more than a few days without improvement
• They come back frequently with no clear trigger
• They are severe or interfere with daily activities
• They are accompanied by swelling of the lips, tongue, or throat
• You have trouble breathing or swallowing

Any signs of anaphylaxis, such as dizziness, severe swelling, or difficulty breathing, require urgent medical attention.

 

How to Prevent Hives

While not all hives can be prevented, there are steps you can take to reduce the risk:

• Identify and avoid known triggers by keeping a symptom diary
• Wear loose, breathable clothing to avoid pressure hives
• Avoid extreme temperature changes
• Manage stress through relaxation techniques
• Use fragrance-free skincare products if you have sensitive skin

 

Treatment Options for Hives

The treatment depends on the cause, but common approaches include:

Over-the-counter antihistamines

These block histamine and help reduce itching and swelling. Non-drowsy options can be taken during the day.

Prescription medications

If OTC antihistamines are not enough, a doctor may prescribe stronger antihistamines, corticosteroids, or other medications to calm the reaction.

Addressing the underlying cause

If hives are linked to an allergy, avoiding that allergen is key. If they are related to an infection, treating the infection should help.

 

FAQs About Hives

1. What are hives?

Hives are raised, itchy welts that can appear anywhere on the body as part of a skin reaction. They may be red, pink, or skin-colored and can change location or size within hours.

2. How long do hives last?

Most hives disappear within 24 hours, but some may last for a few days. Chronic hives can last for weeks, months, or even longer, often coming and going unpredictably.

3. Are hives contagious?

No, hives are not contagious. You cannot catch them from another person, even if their hives were triggered by an infection.

4. Can stress cause hives?

Stress itself does not directly cause hives, but it can make the body more reactive to triggers, which may increase the chances of a flare-up.

5. Do hives always mean an allergic reaction?

No. While allergies are a common cause, hives can also be triggered by infections, medications, environmental factors, or even unknown reasons.

6. What is the difference between hives and a rash?

Hives are raised, itchy welts that change location and shape, while a rash can have many appearances and causes. A rash may last longer in one spot and not always be related to histamine release.

7. Can food cause hives days after eating it?

Most food-related hives appear within minutes to a few hours after eating, but delayed allergic reactions can occur. This is more common with certain medications than with foods.

8. Do hives leave scars?

Hives themselves do not usually leave scars. However, excessive scratching can break the skin and cause marks or scabs that may take time to heal.

9. What is the best way to relieve itching from hives?

Over-the-counter antihistamines can help reduce itching. Applying a cool compress and wearing loose clothing may also provide comfort.

10. Can hives be a sign of something serious?

Yes. If hives are accompanied by swelling of the lips, tongue, or throat, or difficulty breathing, it may be a sign of anaphylaxis and needs immediate medical attention. Persistent hives may also be linked to underlying health conditions.

Conclusion

Hives are a common skin condition with many possible causes, from allergies and infections to stress and environmental triggers. In most cases, they are harmless and temporary, but persistent or severe hives may signal a deeper issue. By understanding the potential triggers, paying attention to patterns, and seeking medical advice when necessary, you can take control and keep hives from disrupting your life.

Knowing what causes hives is the first step toward finding relief. With the right approach, you can reduce flare-ups and enjoy healthier, more comfortable skin.