Although not all Mexicans have it, most do, especially if you are a millennial or even if you were born after the 50s. The reason is that this scar is caused by the vaccine against tuberculosis also known as BCG, which came into use around this time and is administered after birth.
Why does it leave a scar?
The reason he left us one scar is that it is the only one of the entire vaccination scheme, at least in Mexico, that has an application intradermal.
That is to say, it is applied differently from the others, in a more superficial in the first layer of the skin.
The vaccine is applied with the arm stretched out at 45 degrees and inserting the needle between 10 and 15 degrees with respect to the fur to what we know as the dermis, that is why the person who applies it receives training for it.
The scar ends up occurring as a reaction of the body to the vaccine, although there are also cases of people in whom it leaves no trace, because all organisms are different.
The vaccine has to be applied at a very young age
This vaccine has to be applied at a very young age. From newborn children up to 5 years old, and in most cases it is applied in the left arm although it can be applied to the other arm or to the pomp.
In the vaccination record it appears as BCG vaccine. The Ministry of Health (SSA) explains that it is an abbreviation of the two live bacteria of which it is composed, Calmette’s Bacillus and Guérin’s.
The process for the scar to appear
After being vaccinated there will be an immediate response of the body to the vaccine.
Between 10 and 15 minutes after applying it, what we know as a papule should form, which is like a little pink welt, and in theory that happens because the solution you applied is under it.
Doctors describe that in reality the application dose is very small, since it is .1 milliliters for children older than one year and from half of this to less than one year, that’s why the papule is not so big.
After that, it will take two to three weeks for the papule to be removed, and instead be a reddish stain no lump
By the fourth week it will have a hard consistency when touched. And by the sixth week it will begin to swell and form a nodule something like a mosquito bite, that is, a red ball. There it can stay between one or two weeks and the doctors ask to keep the area clean, but not to scratch, rub, or squeeze.
Finally, by week 12, a crust which will eventually fall off and leave the scar.