Talking about urticaria is similar to talking about headaches: both causes and forms vary greatly. The spectrum ranges from short-lasting, mild discomfort to years of constant torment and from clear, easily avoidable triggers to (not so few) cases in which the cause is never found. Also, it is not always easy to identify boundaries between urticaria and other diseases. Some forms of allergies look very much like urticaria, and the processes in the immune system and the body are also partly the same but also partly very different from the processes observed, for example, in connection with asthma, hay fever, or classic food allergies.
The many different clinical pictures of urticaria can be divided according to their duration into acute (less than 6 weeks) and chronic (more than 6 weeks) and into three major groups according to their course:
- the spontaneous urticaria
- the physical urticaria and
- the group of other types
Forms of spontaneous urticaria
- Acute spontaneous urticaria: Hives or angioedemata are formed and fade away after hours or days—at the latest after six weeks.
- Chronic spontaneous urticaria: Hives or angioedemata are formed; the symptoms persist for more than six weeks.
What is spontaneous urticaria, and why do we distinguish between acute and chronic urticaria?
In spontaneous urticaria, wheals and other discomfort occur “out of the blue”, i.e., affected patients cannot predict when the next attack of their disease will occur and they cannot usually consciously trigger such an attack. In spontaneous urticaria every part of the body can be affected.
In acute urticaria, the most common subtype overall, there is a maximum of 6 weeks of discomfort, i.e., acute urticaria disappears within a few days to weeks after the first appearance of hives or swelling of deep skin (often just as inexplicably as it has come). In most cases of acute hives there is a one-time attack that can often cause great anxiety—not least because the symptoms have been completely unknown to those affected up to this time.
Chronic urticaria, i.e., spontaneous urticaria lasting more than six weeks, is very much rarer than acute urticaria.
Subforms of physical urticaria
- Urticaria factitia: Rubbing, scratching, or scrubbing the skin.
- Cold urticaria: Contact between the skin and cold.
- Heat urticaria: Contact between the skin and warmth/heat.
- Solar urticaria: UV light or sunlight
- Pressure urticaria: Pressure
- Vibration urticaria / vibratory angioedema: Vibrations
Other forms of Urticaria
- Physical urticaria: If physical stimuli such as cold, heat, pressure, friction, or light cause hives, specifically of a cold, heat, or pressure.
- Cholinergic urticaria: Raised temperatures (for example, due to hot baths).
- Aquagenic urticaria: Contact between the skin and water.
- Contact urticaria: Contact between the skin and certain substances.
- Exercise-induced urticaria/anaphylaxis: Physical strain.
- No Urticaria: Some diseases appear similar to urticaria and were previously classified together.
In the group “other urticaria”, cholinergic urticaria and exercise-induced urticaria, and contact urticaria are collected. In contrast to that experienced in the case of spontaneous urticaria, the discomfort experienced in connection with these types of urticaria can be brought about deliberately, and the symptoms of these types of urticaria, in contrast to those of physical urticaria, occur independently of physical stimuli.
Cholinergic urticaria
Cholinergic urticaria is one of the more common types of urticaria. “Cholinergic” means that the neurotransmitter acetylcholine plays a role in connection with this form of urticaria. How exactly is currently not known; however, acetylcholine is released from nerves, and activates mast cells with a mechanism that is not fully understood. The most common trigger of cholinergic urticaria is physical (athletic) activity, but fever, stress, hot baths or showers, and even the consumption of too-spicy food or drinking liquor are also triggers. The wheals in cholinergic urticaria are typically smaller than those formed in the case of other types of urticaria and found in the \”welding areas\” (such as the underarms, back) of the concerned persons. Lesions in most cases appear within a few minutes after increasing the body temperature and with the onset of sweating, usually starting at the neck and upper body. After cooling the hives disappear without a trace within minutes to hours.
Cholinergic urticaria can be easily confused with the
- Chronic stress-induced urticaria and
- Exercise-induced urticaria/anaphylaxis
In the case of stress-induced chronic urticaria, physical exertion or a passive raising of body temperature does not lead to hives and itching.
In the case of exercise-induced urticaria/anaphylaxis, physical exertion, as in the case of cholinergic urticaria, leads to discomfort. In contrast to cholinergic urticaria, however, itching and hives are in this case caused solely by physical strain and not by passive heating (e.g. by hot baths).
Therapy
Unfortunately, the underlying causes of most cases of cholinergic urticaria are not known. Treatment of the symptoms (symptomatic therapy) is the only option. With antihistamines or ketotifen or danazol (which is closely related to the sex hormone androgen and should therefore be reserved for severe forms of the disease) or
Hardening: Patients can use the absolute refractory period by triggering an urticaria attack in a controlled manner (e.g. by means of exercise) and then are free of wheals for up to 24 hours. Controlled physical exertion several times daily can prevent the occurrence of pronounced attacks of hives.
Contact urticaria
Here the wheals arise wherever the skin comes into contact with a specific substance (or certain substances). Stinging nettles and jellyfish are classic examples. To be sure, this form of contact urticaria occurs in every healthy person who has the corresponding skin contact. A corresponding response to food or animal hair is less common. Latex, too—especially in health professions—can be the trigger of a contact urticaria. Rarely, cosmetics, or their ingredients (e.g. fragrances) are triggers.
Aquagenic urticaria
Yes, even water can cause hives. However, this is extremely rare. According to the literature, only 35 patients are known worldwide. And the reaction is most likely not really to water in its pure form, the chemical substance H2O, but to the minerals or unknown substances dissolved in the water. Due to the rarity of the disease more precise research is of course extremely difficult. If urticaria occurs while a person is showering or bathing, this should not be considered an indication of “aquagenic” urticaria: usually it is then a case of urticaria factitia (triggered by the mechanical stress of “soaping” or later drying).
ome diseases appear similar to urticaria and were therefore earlier classed together with it. Today we know that other disease mechanisms are behind them, and they are therefore no longer counted as urticaria. These diseases include, inter alia,
- Urticaria pigmentosa (cutaneous mastocytosis)
- Urticarial vasculitis
- Hereditary angioedema
No Urticaria
Urticaria pigmentosa (cutaneous mastocytosis)
This rare disease is an excessive accumulation of mast cells behind the—often brown or brownish—stains and small papules of the skin which can form wheals when they are subjected to friction. This disease usually makes its first appearance in the first few years of life, and often manifests a changing course after a few years. The exclusion of a so-called systemic form is recommended. Treatment of the symptoms is similar to that used in connection with urticaria.
Urticarial vasculitis
This is a vessel inflammation which creates hives and angioedema. This disease basically has little to do with urticaria and is treated differently.
Hereditary angioedema
Due to a genetic disorder in an enzyme (congenital, familial), angioedema may also occur. Antihistamines or corticosteroids do not help here, because histamine is not involved in the development of edemas, and an accurate diagnosis and therapeutic care is usually possible only in specialized centers or by physicians who are familiar with the disease.