I've noted on another post dogs saliva can help make white fur look stained red. My boy over the last week has increasingly scratched more under his belly. I've checked for ticks (has had treatment 3 weeks back) none,no fleas and I can't see any hot spots. He had one last summer and vet gave me some wash for this. He keeps scratching more now. I have read on line you can get  Moist Eczema which can create a hot spot. Dogs can be allergic to grass seeds. We are mainly doing our walks over fields and woods and plenty of wet grass. Could this be a delayed reaction? I always dry him down after getting wet with a towell I  did note we had picked up a different flavour of usual food 9 days ago finished this two days ago. Could this be it? I know ch has popped on in house too but usually not on high and hasn't bothered him before.
I'm just going to use some of the pink stuff I've got left from vets to wash belly.

Any suggestions to stop scratchings? I'm even thinking of buying coat for him if it's grass bothering him. His eating fine and poos are normal.

I  did note we had picked up a different flavour of usual food 9 days ago

Had a xbreed who was going frantic itching, got tablets and shampoo from vets and ended up bathing him at 11pm one night as he couldn't have more tablets and he was really distressed,
He had 1/4 tin of wet with his kibble, we ended up working out that the wet food I had got was in gravy not the usual jelly, swapped back and the itch went.

We have finished the different flavour "Tripe" still in jelly thou. Might skip grass tomorrow and pound pavements. Going through belly area still cannot see a "hotspot'.  I'll keep an eye on his still scratching on and off.

Try.bathing in ether cold tea.black or green or rinsing in dilute apple cider vinegar
  Also u can give certrizene antihistamine 1 x 10 mg tablet per 10 kg of dog just don't tell the pharmisit it's fpr a dog theu can't sell it to you  piriton tje drowsy one is ok as well but I  not 100% on dosage but think it's similar

Thanks furriefriends will try cold tea. I have piraton and his 15.2 kg last check in at vet will break one in half try low dose today.

I would think its the food, I had a lab that couldn't eat tripe in any form or beef come to it, he would break out in sores all over his body. I switched Ted to Natural Instinct (raw) chicken and his skin cleared in days.