Tuberculosis is one of the most dangerous diseases. To get rid of the disease, it is necessary to undergo prolonged treatment, while it is important to identify it in the early stages. Children belong to a vulnerable category of the population, doctors tend to check them regularly by conducting an allergy test called the Mantoux test. It allows you to detect the presence of Koch's bacillus, which is the causative agent of tuberculosis, in the body.
The injection site cannot be wetted, doctors warn parents and the baby himself about this every time the test is performed. But why should water be prevented, and what happens if moisture does get on the skin at the injection site? What else cannot be done until the moment when the redness area is measured? These questions need to be answered.
What happens if water gets to Mantu?
The reason why it is impossible to wet the skin at the injection site is very simple. Liquid can cause swelling. Redness will spread to a significant surface, which will give a false positive result. Additional measures will have to be taken to clarify the situation and make the correct diagnosis, which will force you to spend extra time and nerves. In order not to encounter these and other problems, it is worth doing everything possible so as not to wet the injection site until the doctors take the measurements. Even hands should be washed with care, under the supervision of parents.
How is a tuberculosis test done?
This method of testing for tuberculosis was introduced by the French doctor Charles Mantoux, it is named after him. The test is carried out by intradermal injection of the drug, it is completely safe for the child. The remedy is not living, but destroyed Koch sticks, in fact, this is an extract from them. In antigenic terms, it is completely identical to bacteria, the human immune system recognizes the substance precisely as the direct causative agents of tuberculosis. The reaction of the body to the injected drug allows you to diagnose, determine which of the children is sick and who is healthy. An injection is made in the forearm, into the inner upper part, then a period of 3 days is expected, during which it is impossible to wet the skin.
During this period, the immune system manages to work, at the injection site there is an allergic manifestation in the form of a red spot, which gradually dissolves. After three days, doctors measure the result, noting both the size of the spot and its brightness. If during this period the child wetted the injection site at least once, the result may be unreliable.
Mantoux reaction score
It would seem that the smaller the size of the allergic spot, the better. But this is not entirely true. If it is not, or if the redness is less than 0.5 mm, then there is no protective reaction. Such a situation means that the child’s immune system “does not know” about the presence of this pathogen - this happens when the baby was not given a BCG vaccination in the hospital, or if it was not done correctly.If the spot is more than 5 mm in diameter, additional consultation and examination is necessary to find out if the child is sick or not. It is not necessary to panic right away, since there are a number of factors that can give a false positive result. Despite all the informational content of this diagnostic measure, in some cases it can give an inaccurate result.
In what other cases will the result be inaccurate?
An incorrect result may occur if the child overheats or stays in a stuffy room for a long time. High humidity, steam of a sauna or bath, an attempt to scratch the injection site can change the result and give a false-positive reaction. The same goes for trying to crush the injection site, squeeze the papule. It is necessary to explain this to the child and observe him during the period preceding the test. For most kids, it’s enough to say that if the measures called by the doctor are not followed, a new injection will be necessary.
Interesting fact: some parents believe that by sticking the place of application of the drug under the skin with a band-aid, they can eliminate the influence of water. The opinion is incorrect; under the patch, a false-positive reaction is practically guaranteed.
Is water entering the Mantoux dangerous? What if this happened?
In addition to a false positive result, there are no special hazards. There is, perhaps, a risk of inflammation, if the child bathes in an open reservoir, or dirty water gets into the injection site - microorganisms can get into the wound.The only thing that needs to be done when the child has nevertheless wetted the area of redness is to get the water wet with a sterile napkin. You cannot disinfect this place.
Thus, water entering the Mantoux leads to a false positive result and the need to undergo additional checks. That is why doctors constantly remind that it is impossible to wet your hand before the check, which passes after 3 days.
