Urticaria

The name urticaria is due to Willam, who found a great similarity between this rash and that produced by contact with nettles: urtica urens.

It is an eruptive cutane-mucous disease that affects only the superficial part of the skin and causes well-circumscribed pink lesions, with well-defined borders that can join together to form large welts, accompanied by intense itching.

It can affect any area of ​​the body and appears in outbreaks that last 24-72 hours, so that old lesions disappear as new ones appear.

It can present as a single and isolated outbreak in the life of the patient or cause multiple repeated episodes at varying intervals of time.

Acute urticaria is considered when its duration is less than six weeks.

Causes of hives

Hives can be triggered by a multitude of factors.

In acute cases it is well related to the causative agent, but in chronic cases there are many factors that may be different on each occasion. The causal diagnosis is only reached in 20-30% of cases. It can be caused by:

• Medicines. (The most common in acute urticarias in adults.) The most common are penicillins, sulfa drugs, anti-inflammatories, group B vitamins, and iodinated radiographic contrast agents.
• Food and additives. (The most common in acute urticarias in children.) Mainly nuts, fish, shellfish, eggs, chocolate. As colorants, tartrazine is the best known.
• Infections With almost all bacterial, viral, parasitic and fungal infections, cases have been described. Highlights include the hepatitis virus, candidiasis, and intestinal parasites such as worms.
• Physical agents: cold, heat, pressure, sun … The reproduction of the painting is characteristic when the stimulus is constantly repeated.
• Inhalants The main ones are pollens.
• Synthetic fibers, environmental materials.
• Secondary to other diseases: systemic mastocytosis, tumors, autoimmune diseases …
• Genetically conditioned syndromes. Hereditary angioneurotic edema is due to a deficiency of an immune factor (C1 esterase inhibitor).
• Of unknown cause. More common in chronic urticaria.

By an immunological or non-immunological mechanism, a series of substances are released, among them the best known is histamine , which produce local venous dilation and more or less intense posterior edema that gives rise to the characteristic lesion of urticaria: the wheal.

In general, acute urticarias are immunological and chronic hives are non-immunological.

Immune stimulus

Depending on the way in which they are produced, it can be classified into three types:

• Type I: it is the most frequent. Produced by food, drugs and physical agents. For this response to develop, it is necessary that there has been a previous contact with the causative substance and some time passes for factors to form that will activate and release histamine among other substances upon new contact with the substance.
• Type II or cytotoxic: it is rare. It appears in some post-transfusion reactions.
• Type III or immune complexes: in cases associated with infections.

Non-immune stimulus

• Chemical factors: many substances release histamine through an unknown mechanism, others do so by direct action on cells (morphine, codeine derivatives, snake or insect poisons, bacterial toxins…).
• Physical factors: its form of action is unknown.
• Cholinergic factors: heat, exercise, stress , emotions … can be produced by a reflex mechanism of release of acetylcholine in the nerve endings that give rise to the appearance of mediators such as histamine.

What symptoms appear?

The acute form is very common, affecting more than 25% of the population at some point in their life. It seems to be more frequent in women.

The welts are elevations of less than 1 cm in diameter, pink, surrounded by a more reddish halo, they can be circular, linear, annular, with geographic contours. Evolution is fleeting and with complete disappearance.

The eruption can be localized or generalized and consist of few large elements, or very numerous small lesions. In general, small lesions are associated with food allergies, while larger ones are related to medications.

Acute outbreaks are usually associated with large areas of geographic wheals, while in chronic forms the lesions are small and with little itching.

In children, acute urticarias appear with great edema that produces blisters on the wheal, mainly located on the buttocks and legs.

The most frequent location is the trunk, although the wheal is also located in areas of pressure or friction.

The duration of each injury is a few hours, no new wheals appearing in the same place until at least three or six days later. As new lesions may be appearing in other locations, the rash may last for several days. When it disappears, the skin remains completely normal, except in very acute cases, especially in children, in which there may be an increase in pigmentation (skin color).

The evolution can be very variable. In acute urticaria it is less than six weeks; if it exceeds this period and it is recurrent, we are facing chronic urticaria.

Angioedema

It is a similar way in which the deeper layers of the skin or even other organs are affected. It can appear alone or associated with hives. Its predominant location is on the eyelids, lips, scalp, back of hands and feet. It can be accompanied by edema in other locations such as mucosa of the mouth and pharynx, tongue, tonsils, larynx (causing obstruction and making it difficult for air to pass into the respiratory tract), mucosa of the digestive tract (produces severe abdominal pain), urinary mucosa ( producing a picture of renal colic if it affects the output of the kidney), nervous system and locomotor system.

Treatment of hives

Whenever a drug or food is suspected to be the cause of the outbreaks, it should be suspended. In cases where medications are excluded as the cause, the foods and additives that most frequently cause urticaria should be avoided until the condition is completely remissioned.

When hives are attributable to a specific substance, specific desensitization can be attempted, although the results are highly variable.

Drug treatment

• Antihistamines.
• Corticosteroids: in cases of significant or large edema.
• Hydroxyzine hydrochloride: in cholinergic urticaria.
• Fresh plasma transfusion: in hereditary angioedema .
• C1 inhibitor: in hereditary angioedema.
• Epsilon-aminocaproic acid: in familial angioedema.
• Tranexamic acid: in familial angioedema.

Elimination of etiological factors is the best measure if we know them; if not, the possible appearance of hives is unpredictable.

Before the appearance of lesions such as those described associated with intense itching, a doctor should be consulted to start treatment and suppress the causal factors, which in some cases could lead to extensive reactions that could even compromise life.