Irritating and itching underarms

My pup is just 5 months old and seems to be itching under his arms quite a lot. I have given him piriton which was advised by the vet and been putting a little sudacream on the effected area. He is eating core wellness with a little chicken? Any ideas what it could be or what to try?
Thank you

Has he being running through grass? Katy used to get it that way. The Piriton should help!
You could also try this, it works really well.
https://www.stinky-stuff.co.uk/products/dog-trial-size-non-stinky/

Let us know how you get on

Stinky Stuff is very good. I wouldn't use Sudocrem myself, as it contains zinc which is poisonous to dogs if licked.

I'd also try Piriton & wipe the area with warm salty water after every walk. Hopefully, it's just a grass allergy, but it could also be a food intolerance - chicken being the usual culprit!

An alternative thought - do you use a harness ?
If so, it might be an irritation caused by harness regarding the fit and/or washing product used to wash it ?