Medical expert of the article
New publications
What are allergies?
Last reviewed: 05.07.2025

All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
The human body contains special, natural filters that serve as a barrier to foreign micro and macro organisms, many harmful and even toxic substances. But when the filters are weak, their function is impaired or completely absent, all harmful factors begin their attack on organs and tissues on all fronts. Allergy is a striking example of such an attack. What are these natural filters that are built into our body and protect us from the encroachment of external pathogenic irritants? How does the allergic process arise, and in what directions does it develop? How to avoid allergies and what to do if you already have one?
What causes allergies?
The barrier function in our body is performed by such filters as:
- cutaneous;
- intestinal;
- hepatic;
- immune.
The names of these filters speak for themselves. So, the skin filter is actually our skin. Thanks to this filter, only what the intact skin will allow enters the body. These are solar radiation, oxygen, medicinal or aesthetic-cosmetic substances that are designed for external use and penetration into the skin layers.
The intestines cope with everything foreign by digestion and exposure to high temperatures in interaction with gastric juice. Large protein molecules, when intestinal functions are disrupted, become the main factors from which allergies originate.
The intestines are designed in such a way that when protein gets into them, it breaks down to the necessary amino acid structure and only after that is it used by all organs and tissues as a building block. Unsplit molecules are the cause of the body's sharp reaction to the invasion of a stranger. Hence, such manifestations that are not typical in a normal state: redness, rashes and itching, burning and constant discharge from the nose, spasms, up to respiratory arrest, swelling of the whole body or its individual parts. Severe cases can occur with loss of consciousness, as a consequence of severe intoxication of the body caused by allergens.
The liver filter passes all the blood through itself, taking excess components from it, which is why it more often than others takes the blows that harm the organ itself - the liver. Toxic substances, which our blood is abundant with, settle in the liver filter, are processed by bile and enter the body in a safe form. What is not processed is excreted, what is not excreted remains in the liver ducts, forming stones over time. Allergies occur when the liver has serious failures that may not be immediately detected. Small scale insects, belonging to the flat species, whose favorite place of settlement is the liver, are capable of causing severe attacks of allergic manifestations. These scale insects were given the name "lamblia". They can only be detected by a special analysis carried out on certain days and times, which also requires special preparation.
There is no need to talk about the immune filter for long. Every person knows and understands the principle of our immune system. Everything that is foreign and unnecessary for the body is quickly detected and neutralized. Any weakening of the immune system immediately affects a person's well-being.
The nature of allergies
Each narrow medical specialist sees the involvement of his/her specialized area in the formation of the allergic process. Thus, a neurologist will say that all troubles with the body are based on problems with the nerves, an infectious disease specialist will put the infectious origin at the forefront, and an allergist, the cause-and-effect relationship between antigen and antibody. And, oddly enough, each of them will be right. A therapist and an endocrinologist can be involved in this dispute, and a hygienist will have something to add.
The exact causes and mechanisms of allergic attacks and reactions are still poorly understood. There is an assumption, and today it is the only and priority one, based on the fact that allergies are caused by intestinal lesions. If a person has problems with the intestines, then there is a high probability of his high predisposition to allergies of various kinds.
What are the symptoms of allergies?
The body can react to foreign antibodies violently, quickly, developing rapidly, taking minutes and, in the absence of timely and correct assistance, can lead to a fatal outcome, or it can express minor "indignations" for a long time in the form of malaise, runny nose, constant itching of individual areas or the entire area of the skin. It can be very difficult to suspect a diagnosis that hides an allergy. Therefore, there are often cases when an acute attack of allergy, not noticed in time, turns into a chronic form.
Most often, allergies occur in the form of:
- skin rash;
- pollinosis (its more common name is hay fever);
- Quincke's edema (swelling of the laryngeal mucosa, resulting in spasm of the respiratory tract and large blood vessels, leading to loss of consciousness followed by respiratory arrest);
- bronchial asthma;
- anaphylactic shock.
The symptoms are listed in order of increasing severity. The most dangerous manifestation or even consequence of allergy is considered to be anaphylactic shock due to its rapid development and damage to all vital organs, leading to cardiac arrest and cerebral edema.
How are allergies diagnosed?
It is impossible to get a complete picture and establish the true cause of the allergy based on just one test or one type of examination. In cases where an allergic reaction occurs immediately upon the introduction or entry of a strong antigen into the body with the bloodstream, for example, Quincke's edema can occur instantly, with the bite of any insect, the poison of which a person is allergic to. Or anaphylactic shock - begins to develop immediately after the injection of antibiotics. Here, as they say, the cause is obvious. But what if the allergic reaction occurs periodically and is sluggish, weak, but has an exhausting effect on general well-being? How can we determine what the body is reacting to? Maybe it is house dust playing a cruel joke, or maybe a blooming linden tree outside the window. The cause may be familiar food or a pet. There are so many factors that diagnostic measures must be carried out in a comprehensive manner, and the diagnostic results must be analyzed as a whole. The summary data will provide a more accurate indication of the true cause of the malaise.
When the primary, unspecified diagnosis is an allergy, diagnostics begin with an initial examination of the patient, taking smears from the nasal passages, oral cavity and analysis of all body secretions (blood, feces, urine), taking skin samples, especially from those areas where itching and burning or rash most often appear. A detailed list of all probable and possible hereditary predispositions to allergies, past illnesses, etc. is worked out in detail and compiled. This process of collecting data is called an allergological anamnesis, as a result of which a qualified allergist can obtain complete information about the patient and draw further conclusions based on it.
A sanitary inspection of the home must be carried out. During the inspection, swabs are taken from all surfaces to detect pathogenic flora, air, water, and soil samples of houseplants, if any, are taken. The sleep and rest area is checked, with special attention paid to pillows and blankets. Often, the fillers of these bedding items become the cause of frequent allergic reactions. In addition to the methods already mentioned, instrumental diagnostic tools can be used to assess the internal state of organs, for the presence of diseases, complications, or developmental pathologies, against which allergies may occur.
How are allergies treated?
There is a special group of drugs that are called antiallergens or antihistamines, including Diazolin, Tavegil, Suprastin, etc. However, it should be remembered that these drugs do not remove the root cause, but help relieve symptoms for a short period of time. Each of them has a number of side effects, and the use of drugs should be coordinated with a doctor. At the moment, there are a large number of modern synthetic drugs with targeted antiallergic action with less pronounced side effects or without them at all, but, again, information about these drugs should be obtained from a doctor. The use of such drugs is justified by a temporary effect and in acute stages, their constant use, without finding out and eliminating the root cause, is unacceptable.
Once the underlying cause has been identified, allergies are treated according to well-established schemes, without inpatient observation and often without interrupting the person’s normal lifestyle.