Acute hives are red, itchy bumps or swellings that suddenly appear on the skin. On darker skin, color changes can be harder to see. Hives are often triggered by an allergic reaction, but there can be other causes. Symptoms usually can be relieved by taking antihistamines and avoiding any known triggers.

• If you know what caused the hives, help your child avoid it. If your child gets hives again, pay attention to what they were doing and feeling around that time to help figure out the cause.
• If the health care provider recommended an antihistamine medicine, follow the instructions about how much to give your child. There are different types of antihistamines. Some types (such as Benadryl^® or a store brand) can make small children sleepy, restless, or fussy. In teens, they can make driving unsafe. Other types have fewer side effects. Talk to your child's health care provider about which type is best for your child.
• Place cool wet washcloths on the hives to help relieve itching.
• Have your child avoid hot showers and tight clothing to prevent irritation.
• Discourage your child from scratching or picking at the skin while the hives heal.

• Your child's hives last longer than 6 weeks. Hives that last longer than this are considered chronic (long-term) and might need more treatment.
• There are red areas or blisters with pus around the hives. This could be a skin infection.

Your child has signs of a serious allergic reaction, such as:

• trouble breathing
• throat tightness
• swelling of the lips, face, or tongue
• a combination of two mild symptoms, like hives with vomiting

If your health care provider gave you a prescription for an epinephrine auto-injector, make sure you know how to use it and follow the instructions exactly. If you need to use it, call 911 afterward or go to the ER to see if your child needs further treatment. This is true even if your child is doing better, because there can be a second wave of symptoms. Take the used epinephrine auto-injector with you to the hospital.

Why do acute hives happen? Acute hives, also known as acute urticaria, happen when immune cells in the skin (mast cells) release the chemical histamine. Histamine causes itching, redness, and swelling. 

Causes of hives include:

• infections with a virus (like a cold) or bacteria
• allergies to foods (like peanuts, milk, or eggs), insect stings, or medicine
• contact with heat, cold, vibration, or pressure on the skin
• sun exposure
• stress

Often the cause of hives is not found.

How are hives treated? In many cases, mild hives go away without treatment. The health care provider may recommend an antihistamine or other medicine to help with the itching. Hives may sometimes come and go over a period of minutes to days.

Are hives contagious? No, hives are not contagious. Even hives caused by an infection can't spread to others.