Can a prick test be performed during pregnancy?

No allergy tests should be carried out during pregnancy, including a prick test. This is because the prick test carries a certain, albeit low, risk of anaphylactic shock. Anaphylactic shock is the most severe complication of an allergic reaction and is an acutely life-threatening situation.

Although this complication is very rare, a pregnant woman should not take a risk that is not absolutely necessary. Other milder reactions such as nausea, vomiting, a drop in blood pressure and breathing difficulties can also occur during a prick test. A pregnant woman should not be expected to take these risks either.

What role does histamine play in the prick test?

Histamine is the so-called positive control in the prick test. Histamine is an endogenous tissue hormone that plays an important role in allergic reactions and also in the immune defence. If histamine comes into contact with deeper skin layers during the prick test, it always triggers a skin reaction.

This reaction turns reddish and the skin forms a wheal. The histamine is therefore used to check whether the skin shows any reaction to this messenger substance at all. If the positive control with histamine does not lead to a skin reaction, the result of the prick test can only be consulted with reservation.

Histamine also plays a role in the other test substances used. A classical prick test consists of a positive and negative control, as well as a number of substances known to cause allergic reactions. If a person is actually allergic to a certain test substance, a typical chain reaction is triggered at the skin site.

First, the liquid reaches a deeper skin layer through the prick of the lancet.
There it is then recognized by defense cells, the mast cells.
If there is an allergy to the substance, the mast cells release histamine.
The histamine, in turn, causes the blood vessels in this area of the skin to dilate and the typical redness to appear.
In addition, the dilated blood vessels also become more permeable, allowing fluid to leak into the surrounding tissue.
This mechanism then creates the wheals, which can be perceived as a small swelling of the skin.