Urticaria2017-06-21T22:50:45+00:00

Urticaria

Urticaria (Hives/“bommels”) are reddish pink swellings or “wheals” that occur in crops on any part of the skin. The rash “blanches”: it becomes fainter when pressed by a finger. Each wheal lasts a few hours before fading away, leaving no traces. New hives appear in other places while some are getting better so it looks as if the wheals move from place to place. Wheals can vary in size from 1 mm to many centimetres and may be round or have a wavy border. Hives are usually very itchy.

  • Hives lasting less than 6 weeks is called acute urticaria
  • Chronic urticaria lasts for greater than 6 weeks
  • The causes of acute urticaria may be different from chronic urticaria
  • Urticaria occurs when a chemical called histamine is released from cells in the skin (see what is an allergy)
  • Infections, allergic reactions, chemicals in foods, or medications can cause histamine release
  • Insect bites and certain internal diseases may occasionally be the cause
  • If the reaction is severe it may progress or be part of the spectrum of anaphylaxis
  • Certain infections or parasite infestations cause hives
  • Viral coughs and colds are a common cause in children
  • Almost any drug or over-the counter medication can cause hives
  • Common offending drugs include antibiotics, pain medications and seizure medications
  • If you have an attack of urticaria, it’s important to tell your doctor about all of the medicines that you take to help him/her to find the cause
  • Hives may appear within minutes or up to two hours after eating food(s) that the person is allergic to
  • Hives can also be directly caused by “off” fish, preservatives, colourants and flavourants, and rarely with strawberries and shellfish
  • No routine tests are recommended for acute hives, unless it is part of a more severe anaphylactic reaction (see anaphylaxis)
  • Routine tests are recommended for chronic urticaria, but are limited to very basic blood tests looking for signs of any infection
  • Avoid triggers such as heat, stress and alcohol
  • Your doctor may recommend that you avoid some medications
  • Do not avoid any specific foods unless a specific food allergy has been proven. Your doctor will decide whether to test for food allergies and may have to contact an allergy specialist
  • If suspected, a trial of avoiding preservatives and other additives may be tried
  • Antihistamines given as pills or syrups are the best treatment. All antihistamines are effective, but the older antihistamines can cause you to be very sleepy so are not recommended unless they are the only option available. Newer, “non-sedating” antihistamines are safe to use for a very long time, and are available from a pharmacy without a prescription
  • For acute urticaria or infrequent episodes, antihistamines may be used just as required
  • Patients with chronic urticaria require regular daily use of antihistamines. If regular antihistamines do not stop hives from occurring, your doctor may increase the dose, even up to 4 times that usually given. This can only be done with the newer antihistamines and always under guidance of a doctor. If high dose antihistamines do not control the rash after 2 to 4 weeks, you should be referred to a specialist
  • Some people get urticaria from specific physical stimuli
  • Triggers include light pressure, cold, heat and sweating
  • The wheals of physical urticaria usually last less than 1 hour
  • Cold urticaria occurs during local cold exposure or swimming in cold water. This form can be more severe
  • “Cholinergic” urticaria is caused by heat, stress or fever. These tiny urticarial wheals are intensely itchy
  • Dermatographism (skin writing) is the commonest form of pressure urticaria, caused by stroking /scratching the skin. No treatment is usually required
  • About 40% of chronic urticaria is caused by an allergy to one’s own body
  • People with autoimmune urticaria have antibodies to their own allergy cells that produce histamine
  • They may have swelling of the body as well (see angioedema), and the problem may last for longer and be more difficult to treat
  • It can usually be controlled with the normal medication given at higher doses
  • Angioedema is a deeper swelling of the skin that occurs mostly in the hands and feet, face, genitals and throat. The swelling is more raised than urticaria, less red, and firm
  • It may come and go over a longer period than wheals and last for up to 72 hours
  • Angioedema usually occurs with urticaria, but may occur on its own

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