When you are looking for a dog shampoo there are several things you need to look out for.
1. pH balanced - a dog shampoo should sit closer to a neutral pH level between 5.5- 7.2. Human shampoo generally has a lower pH level so using human shampoo on dogs can lead to itchiness and dryness. Before you purchase a dog shampoo, make sure it is pH balanced.
2. A good dog shampoo should not contain synthetic fragrances. Synthetic fragrances are harsh on a dog's skin, is the number one cause of allergic reactions and dog's dislike the smell and will often roll in the grass to get rid of the scent. Synthetic fragrances often contain toxic chemicals like phthalates, dipropylene glycol and synthetic silicones used to elongate the fragrance on your dogs coat. Look for a product that uses 100% Pure Essential Oils and not just 'tea tree oil' (often a chemical imitation of an essential oil). Some unscented dog shampoos use toxic masking agents to cover the smell of the cleansers, so be sure to find one that contains natural ingredients.
3. Mildness - a good dog shampoo should not contain sulphates or alcohol. Alcohol is used in alot of fragrances, conditioners and some shampoos and dries out your dogs skin. Sulphate based shampoos are very cheap, but are often another cause of allergic reactions for dogs. Many humans are also allergic to sulphates so it is best to stay away from these products, not to mention the side effects. Try to find a shampoo with Ecocert approved cleansers as they are very mild.
4. Additives - the kind of additives used in shampoos are often synthetic so look for a dog shampoo that contains ingredients such as certified organic extracts (non organic extracts often contain residual pesticides), pure vitamins (non acetate), antioxidants like tocopherals (not tocopheral acetate), wheat and oat proteins & bisabolol natural (miracle ingredient for sensitive skin, although sparingly used, if at all as it costs around $1000/kg). Aloe vera is often used in dog shampoo as a mildness additive and aloe vera comes in many forms such as juice, powders and gel. Aloe vera gel is diluted with several ingredients, one of which is alcohol which will dry your dog's skin out and may cause problems with itching.
5. A good dog shampoo will not contain parabens. Parabens are used to preserve cosmetic products and are linked to many serious health issues.
So, how do you know what is in your dog shampoo?
Well, the truth is you may never know as the ingredients in pet grooming products are not required to be disclosed by law. As a consumer, the best you can do is look for a dog shampoo that discloses their ingredients or find one that is sulphate and paraben free with no synthetic fragrances.