There are 2 kinds of hives: acute hives, in which the welts last less than 6 weeks, and chronic hives, in which the welts last longer than 6 weeks. Chronic hives are less understood and may have more complicated triggers than acute hives. Some examples of common triggers include anything that the affected person is allergic to, including foods (especially peanuts and shellfish), drugs, and environmental exposures. Less common triggers include extreme body heat (such as a hot shower) or cold (such as outdoor temperature), some medications, pressure or scratching of the skin, and exercise. Very rare triggers include sunlight, water, and a reaction to adrenaline. Because there are so many triggers for hives, it can be very difficult to identify the correct trigger, and many cases of hives are called "idiopathic," meaning the diagnosis is uncertain. However, because the development of hives may indicate an allergic process, it is important to keep your doctor aware of your hives so that you can be counseled about allergy safety.
- Upper arms or upper legs
An individual hive lesion appears as a well-defined, pink-to-red swellings ranging in size from 2 mm to over 30 cm. Some lesions may develop a lighter center. Hives usually appear in groups or batches.
Individual lesions of hives disappear within 24 hours, though a single episode may last much longer.
Dermographism is a type of hives that appears within a few minutes of scratching the skin. The rash is usually seen in a straight line (linear) pattern.
Swelling of the eyes, mouth, hands, feet, or genitals can sometimes occur with hives. This swelling, called angioedema, usually goes away within 24 hours.
Usually itchy, hives can also burn or sting.
- Take cool showers
- Apply cool compresses
- Wear loose-fitting clothes
- Avoid strenuous activity
- Use an over-the-counter antihistamine such as diphenhydramine or loratadine
In other non-urgent situations, see your doctor if the hives do not improve with treatment or if they continue to appear for more than a few days.
Before visiting your doctor, try to notice what might be triggering your hives and whether it improves or worsens with exposure to heat, cold, pressure, or vibration. Take a list of every medication (prescription or over-the-counter), supplement, or herbal remedy you may have taken recently. Also, recall any recent illnesses you might have had, since some illnesses (or their treatments) can trigger hives.
Obviously, the best treatment for hives is to discover the cause(s) and stop your exposure to them. However, most people with hives do not know the cause, and they require medications to get rid of the hives.
The most common medications for hives include:
- Sleep-causing (sedating) type-1 antihistamines such as diphenhydramine, hydroxyzine, or cetirizine
- Non-sleep-causing (non-sedating) type-1 antihistamines such as loratadine, fexofenadine, or desloratadine
- Type-2 antihistamines such as ranitidine, cimetidine, or famotidine
- Montelukast, zafirlukast, or zileuton