Big Red Bump
If the bumps are more significant, flatter, and don't have a crust, they may be hives caused by an allergic reaction. Usually, an antihistamine and steroids are used to treat them. The swelling caused by an allergic reaction is generally not life-threatening, but it can block the airway, so you should call your vet right away.
Skin That's Red or Itchy
Redness and irritation are often the most common symptoms of allergies in dogs, along with itching. The best way to treat irritated skin is to find out what caused the allergic reaction, whether it was food, fleas, or something in their environment.
While the root cause is being found, you can give your dog temporary relief by using a gentle oatmeal dog shampoo or oatmeal bath to soothe and hydrate the skin.
A hot spot is an area of wet, irritated skin and often has hair matted over it. A dog or cat licking or chewing an area too much can cause hotspots. When the dog licks too much, bacteria get into the hurt skin and cause a hot spot.
Hot spots happen more often in hot, humid climates, and they can sometimes show up after a dog has been in the water or been out in the rain or mud. Also, they happen more often in dogs with thick undercoats.
Simple hot spots can be treated by carefully clipping the are a to let the skin breathe and cleaning the area with a diluted chlorhexidine solution. In addition, you can keep your dog from getting hot spots by grooming it and drying it off after it swims or gets wet.