Unfortunately, we see a lot of orphaned kittens come into our clinic that are infested with fleas. This can sometimes present a challenge because the kittens are too small for conventional topical flea control products such as Revolution (selamectin) or Frontline Plus (fipronil/methoprene). In this case it’s essential that kittens are treated as quickly as possible because anemia caused by fleas feeding on their blood can kill them in no time at all.

Dawn dish soap is safe to use on
teeny-tiny kittens.
Another important thing to remember is that OTC FLEA CONTROL PRODUCTS SHOULD NEVER BE USED ON KITTENS no matter what the label says. This includes shampoos, topicals, powders, sprays, collars and everything in between. If you have a teeny-tiny kitten your best weapons are Dawn dish soap (unscented) and a flea comb (see below).
The Revolution product insert states that the medication is recommended for use in cats eight weeks of age and older. The age limit on Frontline Plus is also 8 weeks. Since we usually don’t know exactly how old our kittens are, we usually go by weight. For kittens, the general rule of thumb is that each pound of body weight equals one month (or four weeks). So, a 1.0 pound kitten is probably 4 weeks old while a 2.0 pound kitten is probably 8 weeks old, 3.0 pounds = 12 weeks, etc.
Capstar (nitenpyram) is labeled for kittens 4 weeks of age as long as they weigh more than 2 pounds. However, I don’t think that’s likely for a kitten so young. However, if you have a kitten that’s infested with fleas and he weighs at least 2 pounds I think Capstar is your best bet. We give this to almost all our orphaned kittens and it’s amazing to watch the fleas die and fall off the kitten in just a matter of minutes.
In case you’ve never heard of Capstar, it’s an oral tablet that kills at least 90% of adult fleas on the host within a period of 4-6 hours. The only downside to the medication is that it only lasts for 24 hours, so readministration is necessary unless you use a product with a longer duration of activity.
For a severe flea infestation, I would give the kitten a Capstar tablet once every 3-4 days until adult fleas are no longer seen and then also administer another long-term product (which lasts for 30 days) to prevent eggs from hatching and developing such as Revolution or Program (lufenuron).
If your kitten is teeny-tiny, your best bet is to purchase a flea comb and comb the fleas out by hand. You can also give the kitten a daily bath using Dawn dish soap. You should lather him up and let the soap soak on his fur for at least a few minutes. Be sure to dry him off well and keep him warm after his bath to prevent hypothermia. If you still see fleas on him after the bath you should get them out with the flea comb.
You also want to make sure to clean the kitten’s bedding daily to prevent the development of eggs, larvae, and pupae in the environment. Vacuum areas where he likes to hang out daily, since vacuuming is a very effective tool for keeping flea populations under control. If you have other pets that are sharing the household with the kitten they should also be treated for fleas.