Dog is licking his underarm/paws! Watz wrong?

Frances Asked: Dog is licking his underarm/paws! Watz wrong?My shihtzu started to lick all his 4 legs. And his skin are red. On his underarm i noticed that some hairs are gone and theres like some flaking on d roots of his hairs. I remember i tried to pick them then some hairs went with it. On his thighs there are some black stuffs (like a birthmark) and he dont have them before. He had his food since he is a puppy and never had a problem with it.I tried to use an anti-flaking and anti-dandruff

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