According to the Daily Puppy, an effective way to get rid of chiggers on a dog is to give the dog a colloidal oatmeal bath. Chigger-infested dogs can be treated by filling a bathtub with warm water and a packet of colloidal oatmeal. The colloidal oatmeal soothes chigger bites and eliminates the chiggers.
Diluted green tea is also ideal for getting rid of chiggers and soothing itchy skin. Simply steep several bags of green tea in hot water. Dilute the green tea with cold water. Use the diluted green tea to bathe the dog.
Many dog owners find that dish soap and Epsom salt baths help get rid of chiggers while also soothing chigger bites on dogs. Bathing a dog in warm water with two cups of Epsom salt will help with any itching. While the dog is in the bath, simply use mild dish soap in place of dog shampoo to get rid of the chiggers. The dish soap will kill the chiggers, but will not harm the dog.
In more aggressive chigger infestations, topical anti-itch and anti-parasite drugs are available for dogs. Aquatic Community recommends seeking the help of a veterinarian if excessive itching occurs. In extreme cases, steroid shots can help with itching.