Hotspot
Is also called acute wet dermatitis.
Hot spots are common with dogs with long hair or a thick coat.

Causes 

It is usually caused by an allergic reaction to a specific antigen. Insect bites such as the flea bites are the most common cause found. But even small wounds in the neck caused by playing are mentioned. There are more possible causes of hotspot such as food allergies, mange, ear infections, poor grooming, shrubs or plants thorns, anal gland disorders, stress, hot weather and hormonal responses.
Hotspots are rare in colder months or in winter. They are equally common with dogs who live indoors and those living outside.

Treatment 

Although this is not a long-term disease. When hotspot occurs, the spot can disappear with treatment within a week. The hotspot could occur again that same summer, the next year or disappear completely.

You should treat the growth of the hotspot and address the original cause.
The area must first be cleaned with sterile water. Dab the area carefully and dry with a clean cloth. Keep the spot dry for a quicker result. There are different kinds of powders and ointments to dry out the hotspot. We must also prevent the dogs from traumatising the spot even further. You can give them a ‘lampshade’ or socks on the hind legs to prevent scratching. Sometimes it is handy to tape the big toe nail of the hind leg with tape like Leucoplast.

Many dogs that repeatedly suffer from hotspots could benefit from regular trimming (shaving) of the coat during the summer. Also a bath with special dog shampoo or defleaing your dog. Regularly cleaning their ears and anal glands can also be a method of prevention. 

Appearance

Hotspots are circular spots, mostly on the head, the neck, the hip and on the side of the body. They are wet, raw, inflamed and usually bare and painful. Dogs usually lick or bite at the spot which causes further irritation. This is why hotspot is also called “Pyotraumatic Dermatitis” due to the fact that the trauma itself plays a major role in the development of the disease.

Hotspot can dramatically change in size in a very short period, what was the size of a quarter can become a spot of 10 cm in 6 hours time.
Always have your dog check by a vet before starting treatment.