The 3 types of skin allergies (and their characteristics)

Allergy is defined as animmune reaction of the body to an agent that is generally harmless to theperson. This clinical picture is usually classified as a situation of “hypersensitivity”, but nothing is further from reality.

The truth is that in allergic episodes the patient’s immune system is acting normally: the error is not in the type of response or its intensity, but in the objective of it, since the causative agent does not constitute a threat in itself to the host.

Allergic processes are increasingly the order of the day, as it is estimated that in school-age children sensitization toat least one allergen is 40-50%. This incidence is increasing continuously between generations, so it is expected that these values will continue to rise over time.

Far from asthma, allergic rhinitis and conjunctivitis known to all, there are other types of allergic processes, and among them we find skin reactions. Because these types of conditions are less known in the general population, today we take this opportunity to tell you about the three types of skin allergies and their characteristics.

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What allergic reactions can occur on the skin?

Skin irritations can be due to a very extensive list of factors, whether they are immune system disorders, medications and infections of viral, fungal and bacterial origin. We must bear in mind that the epidermis and dermis are part of the group of primary immunological barriers, along with mucous membranes, saliva and tears. We are facing our outermost layer, one of the most important organs ofisolation against the environmentand its inclemency.

From cellulite to the chancre of syphilis, we go through almost an infinity of pathogens that can generate damages of different kinds in our skin. Therefore, before any type of skin rash, itching or atypical formation it is necessary to go immediately to a medical professional, since it may be an allergic reaction or another completely different pathology. Of course, an antihistamine will do little against a viral infection, so self-medication is out of the equation.

Once the importance of the skin for the body has been underlined and after having made the pertinent preliminary considerations, it is time to immerse ourselves in the main types of skin allergies and their characteristics. Let’s go there.

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1. Atopic dermatitis

We are facing the queen of allergy-related skin pathologies, since it is estimated that it has a  prevalence of 2-5% in the adult population  and that, generally, 15% of children suffer from it (this is because it occurs in stages very early in development, as up to 60% of cases are diagnosed before the first year of life).

Despite its disproportionate extension in the general population, it is surprising to learn that this pathology remains largely unknown to dermatologists. Its exact cause is unknown, but evidence suggests that it is a synergistic effect of genetic predisposition, environmental factors, immune dysfunction, and alterations in skin permeability.

The symptoms on the skin are clear, since it is a  chronic skin inflammation  over time:

• Blisters that ooze and form crusts.
• Itching that can be severe, especially at night.
• Thickened, dry, cracked and scaly skin.
• Changes in skin color.

Although absolutely not all cases of atopic dermatitis can be linked to allergic processes, it has been seen that 50 to 70% of patients have a history of atopy, that is, a series of allergic disorders mediated by IgE antibodies (responsible for mediating and eradicating pathogens in mammals).

It is of special interest to note that several studies indicate thehigh genetic and hereditary componentof this disease, because if both parents are atopic it is estimated that there is an 80% probability that the child is also atopic. In addition, about 90% of patients with severe atopic lesions have increases in bacterial colonies ofStaphylococcus aureus, a microorganism that produces toxins that worsen the patient’s clinical picture.

It should be noted that one in three people are colonized by this microorganism, but infectious processes occur in cases such as the one that concerns us here, where skin lesions favor its uncontrolled proliferation and a consequent damage to the integrity of the host’s skin.

2. Allergic contact dermatitis

Contact dermatitis is a reddish skin rash that is produced, worth the redundancy, by direct contact with an allergen that activates the patient’s immune system. It isthe most common form of immunotoxicityin humans.

It is necessary to clarify that not all contact dermatitis is allergic, because for example, exposure to harmful agents such as corrosives or toxic compounds can also cause damage to the skin. It is clear that in these cases we are not facing harmless agents that trigger erroneous reactions, because clearly, if we expose our skin to sulfuric acid, it is totally normal for it to suffer.

Seemingly harmless compounds can generate allergic contact dermatitis depending on the individual: adhesives, fabrics, fragrances, nail polish, glovesand an infinity of tools for daily use. This pathology is characterized by a local reddish skin rash (the area exposed to the allergen) that generates itching in the individual.

In addition, readers will be surprised to learn that the first exposure to the substance does not generate an allergic response. Allergic contact dermatitis begins with a first induction phase, where the immune system prepares and sensitizes, and a trigger phase, where the response itself occurs. Thus, the first exposures to the allergen do not generate any apparent reaction on the skin.

3. Urticaria and angioedema

We abandon the complex world of dermatitis, because we can not leave urticarias in the inkwell. It is estimated that these edematous skin lesions are suffered, at least once, by more than20% of the world’s population. This is the case of acute urticaria, since the chronic variant (that is, it remains for more than 6 weeks) is much less widespread. Urticaria is characterized by the appearance of “wheals”, defined as reddish welts that can produce intense itching in the patient.

Again, the exact causes of this reaction are not fully known, but it has been repeatedly linked to allergic processes (widely related to histamine) to food or medications. Even so, not all hives are caused by allergies, as “non-immune” variants can occur due to cold, sweating or exposure to certain viruses and bacteria, as well as irritants.

It is necessary to note that acute urticarias correlate in many more cases with eventual allergic processes (for example, eating a food), while chronic cases are not usually linked to this type of immune responses, since it is difficult to attribute the clinical picture to a specific trigger.

Angioedema is a pathology that shares several characteristics with urticaria, but differs from the latter in that the lesionoccurs under the skin and not on it. It is known that angioedema is also related to allergic processes by the concentration of histamine in the blood, a substance released in events of this nature.