Hives, the common term for urticaria, may appear as blotches or raised red bumps (wheals), caused by irritation in the upper layers of the skin. They can be pale or red in color and are very itchy. The bumps are often oval or round, but also can be other shapes. They are usually 1 to 2 cm in size (about the size of a quarter) but can be larger. They may combine with nearby hives as they grow to form larger hives. The individual lesions usually disappear within minutes to hours but may return elsewhere. Once faded, they leave no marks other than scratches from itching. They may come and go for days or weeks, sometimes longer. In most cases hives are not due to a specific allergy. When hives occur most days for more than six weeks this is defined as chronic urticaria.
Hives are common. Up to 1 in 5 people (20%) of people will develop hives at some time during their life. However, in only 1 in 100 (1%) will they last for over 6 weeks. In most cases, hives are not due to allergy. Underneath the lining of the skin and other body organs are blood cells known as Mast cells. Mast cells contain natural chemicals including histamine. When these are released into the skin, they irritate nerve endings to cause local itch and irritation and make local blood vessels expand and leak fluid, triggering redness and swelling.
Hives can also cause deeper swellings in the skin, and this is called angioedema. These swellings are often bigger, last longer, may itch less, sometimes hurt or burn and respond less well to antihistamines. Large swellings over joints, for example, can cause pain that feels like arthritis, even if the joint is not involved. Angioedema most frequently affects the face and lips. Although hives and facial swelling can be uncomfortable and cosmetically embarrassing, they are not usually dangerous. Rarely, angioedema (swelling) occurs without hives. This may suggest a special situation requiring additional evaluation.
Hives are rarely due to a serious underlying disease. Often the cause of hives in not obvious. Infection from a virus is the most common cause of hives in children. Contact allergy to plants or animals may cause localized hives. Allergic reactions to food, medicines or insect stings can appear as hives. They usually occur within one to two hours of exposure and disappear in most cases within six to eight hours. An allergic cause may be suspected if episodes are rare, short-lived and occur under specific circumstances (e.g., Only when exercising, always within two hours of a meal or when symptoms involving other organs occur around the same time, such as stomach pain, vomiting, difficulty breathing or dizziness).
Chronic urticaria is defined when hives occur most days for more than six weeks. Symptoms of chronic urticaria usually resolve, although this can take months or several years. Chronic hives can last for many years but will often go away. In these individuals, hives will resolve in half of patients within 1-2 years and 80-90% of patients will improve within 5 years. Even if a patient’s hives improve, it is not unusual to see the hives recur months to years later. Ongoing hives lasting days at a time are almost never allergic in origin. Usually, the cause of chronic urticaria cannot be identified. The absence of an identifiable trigger can be frustrating for patients. Stress is a very rarely the cause of hives but may make the symptoms worse. In some people hives are caused by physical triggers, including cold, heat, sunlight, vibration, rubbing or scratching of the skin (called dermatographism), and delayed pressure (such as after carrying heavy bags).
Most people with hives do not need allergy tests. Tests are sometimes done when hives go on for long periods of time, or when unusual symptoms are occurring around the same time. This is to exclude other diseases, which may appear as hives first. If hives are associated with high fever, bruising, bleeding into the skin, purple lumps that last for several days, or sore joints, a doctor’s appointment should be scheduled. Allergy testing is performed when the history suggests an allergic cause.
Treatment may not be needed if the hives are mild. They may disappear on their own. To reduce itching and swelling consider the following: Do not take hot baths or showers; Do not wear tight-fitting clothing, which can irritate the area;). Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided as they can make symptoms worse. Non-sedating antihistamines such as Allegra (fexofenadine), Zyrtec (cetirizine) or Claritin (loratadine) are often used to reduce the severity of the itch and reduce hives. Medications will not “cure” hives but may help to completely resolve them. Antihistamines are the best initial medication to treat your hives. Sometimes, a combination of several antihistamines or an increased dose of one antihistamine may be recommended. Corticosteroids, such as prednisone may help hives. These are not an ideal treatment for long-term use but may have a role to relieve severe symptoms for a few days. Other oral prescription medicines may be needed, especially if the hives are chronic (long-lasting). For those with chronic hives that do not respond to these therapies injection therapy with Xolair (omalizumab) may be an option that is recommended.