Patchy hair loss on hindquarters

[MagicMelon]

My Welsh Cob is allergic to numerous things (but is on a vacc course). Normally his allergies just cause him to rub his lower mane out, but he did come out in huge welt-like lumps all over his chest and neck last year. I noticed yesterday that he's got small areas of patchy hair loss on his hindquarters along with 3 little lumps like insect bites - its not that noticable as he's very dark bay. But Im unsure if this is just another allergic reaction, or if its something else? Its nearish the top of his tail but further up so its not like he could have itched it out (and his tail hasnt been touched). It cant be rainscald since he gets a rug on every time it rains! It doesn't bother him if I touch the areas.

I plan to wash it today with Tea Tree shampoo. But any ideas? Im just worried in case it gets worse as he does showing so its not a good look!!

 

[Box_Of_Frogs]

Could easily be lice. Look for tiny white specks that look like bot eggs crawling slowly in the hair. Tea tree shampoo won't touch them if it is lice - you need Frontline.

 

[MagicMelon]

Would lice cause something like this though? He's very dark bay (ie. black) so I would expect white specks to be obvious but Ive found nothing like that?