Insect bites and nerves

[DaveC426913]

This is an academic question - out of curiosity - not so much about actually getting relief.

I've got a nasty mosquito bite on the under side of my forearm. It's a Muskoka mosquito - the big ones with the really itchy bites.

Even if I don't scratch it, it still rubs on everything from desk edges to couch cushions. It is transferring the itch along my nerve to the knuckle on my thumb, which is now also very itchy.

I am applying an anti-itch cream to the bite itself, but it's not enough to stop the itching. My knuckle still itches terribly.

So here's my question:

Does the application of an anti-itch cream to the site of the deferred itch have any effect? i.e. does an anti-itch cream only work against the actual site of nerve inflammation? Or can it work on a secondary spot that is only irritated by proxy?

 

[phinds]

Wow, that's wild Dave. I'd never heard of a secondary spot itching from a bit elsewhere. I don't see how the cream would do anything except at the bite site, but then I don't really know what I'm talking about, as usual.

 

[Dr Aaron]

It really is not that complicated. The brain only notices what the nerve tells it. The site of the bite is the source of the irritation, both directly at the site of injury and at the referred site. The brain senses the referred site of itching because the nerve became irritated by the bite. The brain tends to assume that whenever a certain nerve fires, it is related to the location at the distal end of that nerve.
If you hit the ulnar nerve at your elbow (the "funny bone") when that nerve sends its signal to the brain it will be interpreted as coming from the nerves running down the forearm and fingers. The brain is being fooled into analyzing the nerve's message incorrectly.
For the bite, the irritation at the immediate location can irritate the nerve going to the "referred site". Since the irritation is at that specific location of the bite, that is where the cream will do the most good.

 

[Lonnie Klein]

Thanks for creating the awareness here Dr Aaron.

 

[DaveC426913]

It really is not that complicated. The brain only notices what the nerve tells it. The site of the bite is the source of the irritation, both directly at the site of injury and at the referred site. The brain senses the referred site of itching because the nerve became irritated by the bite. The brain tends to assume that whenever a certain nerve fires, it is related to the location at the distal end of that nerve.
If you hit the ulnar nerve at your elbow (the "funny bone") when that nerve sends its signal to the brain it will be interpreted as coming from the nerves running down the forearm and fingers. The brain is being fooled into analyzing the nerve's message incorrectly.
For the bite, the irritation at the immediate location can irritate the nerve going to the "referred site".

Yes, all as I surmised.

Since the irritation is at that specific location of the bite, that is where the cream will do the most good.

No question about where it will do the most good; I was wondering if treatment at the deferred site would do anything (since treatment at the primary site was insufficient).

 

[Dr Aaron]

Thanks guys but we are all here to learn and teach. Treatment at the distal site of the perceive nerve sensations will not do any good. If the local treatment at the bite location did not work, you need a better treatment there. The cause of the symptoms is inflammation at the site, so using Hydrocortisone is better than using a Lidocaine-containing cream because the Lidocaine can give temporary numbness but will not alter the course of inflammation. Topical Benadryl cause reduce the response of the tissues to Histamine, but that still leaves leukotrienes, cytokines, etc. to keep the inflammation going. When a person is having a heart attack, they often have referred pain to the neck/jaw and the left arm. Treating those referred symptoms don't do a whole lot to stop the heart attack itself. Treat the problem, not the symptoms!

 

[CazT]

Could I continue this rather old thread as I have a similar but slightly different experience? I had a very itchy, small bite on the underside of my wrist so I used anthistamine cream several times to soothe it. It disappeared within a couple of days but was immediately followed by something that feels like nerve pain down the outside of my wrist and over the top of my hand, a kind of burning sensation which is really quite bothersome when I use my hand. Could this be coincidental or is it likely to be due to the bite? If the latter, would hydrocortisone cream on the bite area help? There is no visible inflammation and the bite is barely visible now.

 

[berkeman]

Could I continue this rather old thread as I have a similar but slightly different experience? I had a very itchy, small bite on the underside of my wrist so I used anthistamine cream several times to soothe it. It disappeared within a couple of days but was immediately followed by something that feels like nerve pain down the outside of my wrist and over the top of my hand, a kind of burning sensation which is really quite bothersome when I use my hand. Could this be coincidental or is it likely to be due to the bite? If the latter, would hydrocortisone cream on the bite area help? There is no visible inflammation and the bite is barely visible now.

Welcome to PF.

We've tightened our rules about offering diagnoses on PF, so this thread will be closed off now, and please see your family doctor to discuss this and have some tests run. Be well.