Dog skin conditions are unfortunately all too common. Some allergic reactions can cause incessant scratching, licking, chewing, and fidgeting; making life so uncomfortable for him. They can also give way to hair loss and painful lesions that become infected without proper care. Here are the most common causes of skin conditions, often known as dermatitis according to PetMD in your furriest family members.

Environmental
Dogs sometimes develop a sensitivity to lawn grasses that produces itching. Moisture that gets trapped on the skin can also cause pets to develop skin lesions known as "hot spots," which are especially common to dogs with thick coats, as well as long coats that are prone to matting.
Environmental factors such as dust, mold, pollen, mildew, and other airborne allergens might also make your dog itchy and uncomfortable, resulting in painful lesions and hair loss. Keep in mind dogs can develop sensitivities to perfume and cigarette smoke too.
Nutritional
Food allergies are fairly rare in dogs, but when allergies do occur, the condition is usually caused by the proteins contained in beef, pork, lamb, chicken, eggs, and fish, as well as plant-based proteins from wheat. Beef, dairy, and wheat tend to contribute the most problems for dogs.
The main symptom of nutritional allergies is skin irritation and excessive scratching, but you may also notice your dog experiencing digestive issues such as vomiting or diarrhea. No matter what the side effects, it's best to call your veterinarian if you notice him coping with any of these issues.
Parasitic
Dogs can develop an allergic reaction to flea bites, which is actually an immune response to flea saliva known as parasitic dermatitis. This can cause excessive itching, inflammation, and hair loss.
Although fleas are the most common cause of parasitic dermatitis, tick bites can also trigger a similar reaction in dogs. The exact cause of parasitic dermatitis in dogs can be hard to pinpoint as they're also prone to skin reactions from various types of mites, such as Cheyletiella mites or scabies. If treating your dog's fleas and ticks doesn't do the trick, check with your vet to see if your dog has a mite infestation.
Infectious
Dogs can also develop infectious dermatitis, which is caused by bacterial, fungal, or yeast infections. One common cause is fungi called dermatophytes, more commonly known as "ring worm." Another is a yeast infection called Malassezia pachydermatis, which might be secondary to other health problems. In addition to treating any underlying medical conditions, antibiotics or antifungal medications are typically prescribed to address this form of dermatitis.