How does afterbite work?

[Talcite]

I know afterbite's active ingredient is ammonia. How does it stop the itch from an insect bite though? Anyone have an explaination that's biology-chemistry centered?

 

[Gibsons]

Originally posted by: Talcite
I know afterbite's active ingredient is ammonia. How does it stop the itch from an insect bite though? Anyone have an explaination that's biology-chemistry centered?

I'm not entirely sure, but I suspect the ammonia denatures the the toxins - toxins in venoms are usually enzymes (lipases for instance) and they can be denatured by different solvents.

Meat tenderizer can be effective against some stings for similar reasons. It cuts the enzymes/toxins apart rather than denaturing though.

 

[Talcite]

I always thought the 'itch' from a mosquito bite was an immune response?

 

[Gibsons]

Originally posted by: Talcite
I always thought the 'itch' from a mosquito bite was an immune response?

For the most part, yes, that's why antihistamines work. Ammonia may have some some immune suppression properties at high concentrations. Like I said above, I'm not completely sure.

I'm basing my guess on meat tenderizer, I know it works on some stings, and I'm pretty sure its mechanism is degrading the toxin, not immune suppression. I think for bee stings and the like, immune depression wouldn't stop the pain and swelling - the enzymes in the venom do Bad Things directly. Some venoms are neurotoxins, phospholipases, etc. IIRC.

I did a decent little pubmed search on the topic and only found one article directly mentioning ammonia for stings, but all I could get was the abstract (it was published in 1980).