Pemphigus

Pemphigus is an autoimmune disease (where the body mistakenly forms antibiotics against parts of itself), which affects the blood supply to the nail bed. The nail separates at the quick and falls off.
Symptoms
Clinical signs are a swollen nail or a loss of pink coloring along the center of the nail. The nail becomes soft, crumbly and grows with a shape change. Pus and a foul odor are common. The dog may lick the nails or limp. This condition can be confused with a simple bacterial or fungal infection.
Treatment
Both topical and oral treatment can be used. Your veterinarian can prescribe antibiotics and antihistamines. Tetracycline/Niacinamide and Rimadyl are recommended. Treatment must extend over several months.
Preventative
Vitamin E or fish oil tablets are a good preventative. Derm Caps ES and 3V HP Caps can also be used.