Dog dermatology

My one year old Spring has orange/brown colouration in patches- largest 8x4" on his back, chest and neck. They have been present since about 4-5months old. I feel he goes through periods of excessive shedding but has no bald patches. No lesions in groin or foot concerns. We are waiting to see a dermatologist but still have another years wait! Hoping to shed some light on the cause so we can address it.  there is no malodor, crusting or dandruff and he doesn't appear itchy at these sites

Hello!  If your vet has arranged a skin referral, I would presume that they have already tried to rule in or out various conditions?  Good questions for them include, what have you managed to Rule out so far?  What could this still be that you could rule out in this clinic?  It could be that they have tried to rule in or out everything that they know.  I wonder about hormonal changes?  As a vet, I used to find that speaking to laboratory pathologists could prove very useful in investigating differentials.

One that jumps into my head is polyphyrin, a brown pigment that is found in drool when a particular area of the body is licked.  This can occur in allergy eg to a couple of fleas picked up in the environment (not enough to 'see' very easily) or to a particular pollen etc.

Yeast infection, bacterial infection and changes to a dogs' hormones may be included in the other contenders.