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Taking antihistamines is common for relieving the itch sensation from a mosquito bite. This itching sensation is one of the side effects of histamine, which is produced as part of the immunological response.

In this answer How do antihistamines work? it is claimed that antihistamines won't have any effect in the immunological system, as it just blocks the symptoms/effects of histamine itself. But these effects are needed for certain type of immunological response, for example vasoconstriction to increase vascular leakage, to allow for increased access into the affected areas (I assume).

Is blocking the effect of histamines actually counterproductive in the healing process of an itching insect bite?

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  • There really isn't any appreciable wound to heal in the context of a mosquito bite. Aug 24 '20 at 17:44
  • @BryanKrause so would you argue a mosquito bite never heals? What would you call the process of its disappearance?
    – hirschme
    Aug 24 '20 at 18:31
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    Just takes a bit for the proteins in the saliva to clear out and the inflammation to go away. There's some minor injury too but I don't think that has much if any relationship to the time during which you experience the symptoms of a mosquito bite. It's just an immune response, which is why if you don't scratch it seems to not be nearly as bad. Aug 24 '20 at 18:34
  • @BryanKrause that makes sense. So really the "healing" is not much of a direct action by an immunological response, but just simply a washing away of the foreign bodies that triggered the response. In that case antihistamines should not have any negative effect in the "healing" time (unless the washing away is affected by the immunological response). Btw I think that could qualify as an answer to the question instead of a comment
    – hirschme
    Aug 24 '20 at 18:38
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    I think it won't be easy to answer your specific question much at all, because recovering from normal mosquito bites themselves is not really an issue of much medical significance. Clearing up foreign material is an immune function, but that doesn't mean it's affected by antihistamines in the doses used. Thomas has provided some sources for plausible impacts on healing more generally, but these have little to do with mosquito bites. Aug 24 '20 at 22:37
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On histamine: Histamine causes vasodilation, not vasoconstriction. The amount of histamine blocking agents ingested largely will not counteract the whole effect of histamine, however it may prevent more pronounced side effects that are not appreciated. One of these side effects, by vasodilation and vascular leak is edema. Edema can produce pressure on capillaries and further reduce perfusion of affected areas. Some more information on histamine: https://en.wikipedia.org/wiki/Histamine

There are some data that hint at what you are suggesting, namely that some growth factors are accelerated by histamine (albeit the paper is on mice): https://www.sciencedirect.com/science/article/pii/S0022202X15329146

A very old paper on the role of histamine in wound healing compared durability of keloid tissue: https://pubmed.ncbi.nlm.nih.gov/1791057/

The study did not use OTC antihistamines however; they found though that exogenous histamine applied topically reversed the delayed healing induced by the experimental antihistamine. This may or may not be due to the increased proliferation of cells, growth factors or increased perfusion where previously it was inhibited.

Finally, in https://en.wikipedia.org/wiki/Wound_healing it is described how histamine allows inflammation communicating cells etc. to leave blood vessels, which are needed in wound healing e. g. for removal of dead tissue.

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  • thank you for the links. If I understood correctly, you are suggesting that there are enough reasons to think antihistamines can actually delay the healing process / removal of tissue?
    – hirschme
    Aug 24 '20 at 20:36
  • It's not really important what I think in this context. My opinion wouldn't shift any statistical inference people have previously found. However, what I have found in the short time I have searched for, are old studies that are not directly investigating what you are looking for. I would not say it is a good idea to draw inference from this other than opinions albeit on a small amount of investigative footing. TL;DR: With this little amount of data, any conclusion will be mostly opinion based (how much you trust old, indirect answers etc.).
    – Thomas
    Aug 24 '20 at 20:44

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