Some products that kill fleas on dogs can also be used on puppies as young as 4 weeks. For pups younger than 4 weeks, you will need to groom your puppy with a flea comb, or pick fleas off with a tweezers. Be sure to keep the pups warm while you're working with them; wash the bedding; vacuum the surroundings; and treat the mother.
Fleas can remove enough blood to make puppies anemic, so confirm your pup's gums are pink.
Watch for rice-like dried tapeworm segments at the rectum or in the stool in the next several weeks because fleas carry tapeworms.
Some flea control products may fit in both categories. Flea control products that affect flea eggs and larvae are called insect growth regulators (IGRs). IGRs are effective in controlling a flea infestation because they prevent flea eggs and larvae from developing into adult fleas. This process helps to end the flea life cycle, and reduces the risk of future flea infestations.