What is urticaria?
Urticaria, or hives, is truly not one disease but a reaction pattern of the skin. It is a vascular reaction representing localized edema (swelling) caused by dilatation and increased leakiness of the blood vessels of the skin. It manifests as an itchy, red, and raised rash. Urticaria has many causes and can be divided into acute and chronic forms. The chronic form is by far the more difficult clinical problem.
What are acute and chronic urticaria?
The definition of chronic urticaria involves daily or intermittent hives for greater than 6 weeks. Acute urticaria has lesions that last less than 6 weeks and is likely a distinct disorder. Compared to chronic urticaria, acute urticaria is usually easier to control with medication. The cause of urticaria varies and, in many cases of chronic urticaria, it is unknown. It is estimated that up to 90% of the times in chronic urticaria, the etiology is not identified.
What causes urticaria?
Urticaria can be mediated by both immunologic and non-immunologic factors. Hives are formed by blood leaking out of small blood vessels in the skin. This is caused by the release of a chemical called histamine. Histamine is released from cells called mast cells which lie along the blood vessels of the skin. Allergic reactions, chemicals in food, medications, and physical factors (cold, heat, sunlight, water, pressure, and vibration) can cause histamine release and lead to hives. Many times, however, it is impossible to find out why the hives are forming. Below is a list of items that can cause urticaria in certain individuals.
- Drugs: Aspirin, Ibuprofen, Opiates, Penicillin, Insulin
- Contacts: Latex, perfumes, wool
- Foods: Tree nuts (e.g., walnuts), peanuts, fish, crustaceans, bananas, soybeans, tomatoes, eggs, milk, berries, wheat
- Physical Factors: Simple friction or scratching, sunlight, pressure, heat, cold temperature, water, vibration
- Inhalants: Latex, dust mite, animal danders, pollen
- Infections: strep throat infections, yeast infections, sinus infections
How is urticaria diagnosed?
Urticaria is usually diagnosed by the physician based on the symptoms described and the appearance and distribution of the rash. No specific testing exists.
Ideally, the causative factor is identified; however, many times, this is not possible. Your physician may provide you with a questionnaire that may help identify the specific agent. In addition, laboratory tests may be ordered in trying to identify the cause in chronic urticaria.
How is urticaria treated?
Eliminating the causative agent is the best way to treat chronic urticaria. When the cause of chronic urticaria cannot be found, drug therapy enables most patients to live normal lives. It is important to note that the medication should be taken as prescribed instead of on an “as needed” basis.
In the great majority of cases, the lesions of chronic urticaria can be controlled with oral antihistamines. A “non-sedating” antihistamine (loratidine, fexofenadine, cetirizine) is often the first choice since they have minimal side effects and are quite effective in most cases.
When these drugs fail, a trial of “classical” antihistamines may be tried. Hydroxyzine, diphenhydramine, and doxepin may be used. These drugs are quite effective but are often found to be sedating. Tolerance to the sedative effects of these medications may occur after several days.
An occasional patient may need corticosteroids. Cortisone and its derivatives can be used safely during severe episodes, or when you particularly need to be clear, such as for an important social event or business meeting. However, because of their severe side effects, the use of steroids is limited to brief periods.
How does the disease progress?
In most instances there is one final consolation. The illness seems to subside as spontaneously as it appeared. Thus, even though a cause may not always be found, nature usually has its own way of eliminating the problem. You can expect to eventually get relief, but it is difficult to predict when it will happen.