Once you notice your dog itching, check for fleas and ticks first. These blood-dependent pests use dogs as hosts all the time and can latch on anywhere. Ticks can go unnoticed for some time until they become fully engorged and large enough for you to spot and remove. Keep in mind these irritating insects can and do carry a variety of dangerous diseases, so it's important to check for them during tick season and any time your dog enters a potentially infested area (anywhere outside, mind you). If you find a tick on your canine and need help removing it contact your veterinarian.
Fleas are less dangerous but just as uncomfortable. Infestations of this kind can lead to itchy skin in dogs and other skin reactions, requiring veterinary care. Certain dogs can have allergic reactions to flea bites that cause very painful hot spots, hair loss, swelling, and even infection. Spotting them is sometimes easier than ticks if you check regularly, but in long-coated and dark-colored dogs you might need some extra help. Brush through your dog's coat with a clean flea comb to be sure you're dealing with a flea occupation. Flea dirt can be spotted on your dog or in his most common resting areas such as beds and crates. If you give your dog a bath and notice a reddish-brown color in the water, fleas are almost always the cause.