Welcome to our weekly 'Ask a Vet from the SF SPCA' feature on 7x7.com. They've enlisted their Co-President, Dr. Jennifer Scarlett, to answer your questions every week. Got a question for Dr. Scarlett? Ask away in the comments!

Q: We do not treat our 5-year-old Maltipoo for fleas - and he never has problems. Recently though, we visited another household with two other dogs, both treated with flea medication. After a day-long visit, our pooch had fleas all over him and the other dogs were still flea-less. Why did that happen?

A: Gotcha!  As compared to days gone by when it was common to use organophosphates on pets the products available now to prevent and control fleas are great.  Even the best products like Advantage, Frontline and Comfortis are not perfect—so they may kill 95 to 99% of the fleas, but they don’t stop flea eggs from hatching.  Many of the old pyrethrin based products are much less effective.   The problem might not stem from the dogs themselves, but from the environment. Flea eggs can hang around in the nooks and crannies of a house and continue to hatch, develop and feed on pets and people.  Most likely some of the fleas that were newly hatched from the eggs in the house had a feeding frenzy on your virginal pup!  I recommend one of the newer effective flea medications—the new long lasting oral product is my favorite. You’ll need to see your vet to get it, but it is reasonably priced. Oh, and if your dog brought fleas home, then the bad news is that they're still there.  You’ll need to use a product that has an insect growth regulator to kill the eggs they laid in your house and get rid of them. You can call our pharmacy – we carry a really good, non-toxic powder. Fleas are tough little buggers.  Good luck.

You have questions? We have answers! No question is too silly or too gross…we’ve heard it all! “Ask A Vet” every Friday from 12pm-1pm on Twitter: @sfspca.