Chronic hives - Causes of chronic hives

Skin sensitivity > Chronic hives causes

Urticaria, also known as hives, appear as pink-red welts (wheals) on the skin and are usually itchy. Generally the causes of chronic hives are allergic reactions triggered by food, chemicals, physical stimuli or drugs.

On many occasions the causes are not known or idiopathic.

Hives is considered chronic when the swelling and redness persists or recurs for more than six weeks. The lesions of chronic hives are pink-red and appear as well-marked raised swelling. The lesions may appear round, oval or as generalized raised plaques. Some papules may be disappearing while new ones appear. In chronic hives this may go on for days together. Scratching causes new papules to appear.  In some individuals chronic allergy may resolve after a few weeks whereas in some individuals it may last or recur for years. Image describing the role of mast cells
in an alleric reactions in chronic hives

The causes behind chronic hives formation

The immune system is behind the allergic reactions resulting in hives. Our body's immune system being a system of biological structures and processes, is responsible for detecting a wide variety of invading pathogens, from viruses to parasitic worms and providing protection from them. The immune system has to distinguish the invaders from the organism's own healthy tissue and also other harmless substances. Inflammation is the first response on encountering infecting pathogens and causes increased flow of blood to the affected tissue which in turn causes redness, swelling, warmth, itching and pain.

Mast cells are resident cells of several types of tissues like connective and mucous tissues. They contain many granules rich in histamine, cytokines and heparin and regulate the immuno-inflammatory response. When activated mast cells rapidly release preformed mediators from granules like histamine, serine proteases, serotonins and heparin; various hormonal mediators like newly formed  lipid mediators, cytokines and Eosinophil chemotactic factor are also released into interstitial spaces.  Histamine by activating the endothelium and dilating capillary venules causes plasma to leak into interstitial spaces. This in turn causes edema, reddening, warmth, itching and pain. A cascade of other immune reactions follow to eliminate the pathogen.

However in some persons the immune system may get sensitized to harmless substances and set off allergic reactions. When the immune system mistakenly recognises the body's own tissues or other harmless substances as invaders, the mast cells release histamine and other chemicals and cause allergic reactions culmulating into chronic hives papules. Certain chemicals released in this process sensitize nerve endings making the affected area sensitive and itchy.

Allergins are causes of chronic hives in prone individuals

• Some drugs and medicines are causes (penicillin, sulfa drugs).
• Many chemicals, pesticides and detergents are causes of hives.
• Marine and fresh water foods like fish, lobsters and shellfish.
• Foods of animal origin like egg and milk are causes allergy in some individuals.
• Plant foods like peanuts, brazelnuts, walnuts and certain vegetables are the reasons.
• Animal dander, dust and dandruff.
• Insect bites, insect stings and insect waste (bedbug bites, mite bites, mosquito bites, scabies).
• Pollen, husk, bran and other plant products.
• Mental stress and emotional disturbances.
• Exposure heat or extreme cold.
• Exposure to sun.
• Exercise and perspiration.
• Many infections and diseases like lupus, thyroid disease, other autoimmune diseases, herpes and leukemia are causes for hives.
• Helicobacter pylori may function as a trigger of chronic hives.

Chronic idiopathic hives and autoimmunity

Many of the chronic cases of hives are idiopathic i.e. have no known causes. They are mostly due to autoimmunity. They have been found to be associated with other autoimmune diseases. About 33% of the patients with chronic idiopathic hives were found to have functional autoantibodies.

"If the conditions are affecting the throat, inner mouth or inner throat an emergency situation of life threatening respiratory stress and anaphylaxis may follow and hospitalization is immediately required."

Whatever be the cause of these chronic hives, there are first and second generation antihistamines and corticosteroids available for control and treatment of papules.

Topics of interest:
Chronic hives treatment
Types of hives

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References:
1.Prussin C, Metcalfe DD (2003). "IgE, mast cells, basophils, and eosinophils". J Allergy Clin Immunol 111 (2 Suppl): S486–94. DOI:10.1067/mai.2003.120. PMID 12592295.
2.Novembre E, Cianferoni A, Mori F, Barni S, Calogero C, Bernardini R, Di Grande L, Pucci N, Azzari C, Vierucci A. hives and urticaria related skin condition/disease in children. Eur Ann Allergy Clin Immunol. 2008 May;40(1):5-13. PMID: 18700329.