Since my dog was groomed last week she’s been biting at her legs. I have washed her legs since, but she’s still biting.
No sign of fleas.
Can I give her antihistamines and, if so, what dose for approx 4kg toy poodle ?

I'd talk to the groomer perhaps re what shampoo was used, or whether any shaving was done which could be irritating her.   Before you resort to using antihistamines.   I use Piraton, but not for any dog as small as 4kg.   I think you also may need to speak to your vet re dose if you go down that road.

Her legs weren’t shaved and it’s her legs that she’s nibbling at.
I’m not sure whether to put a flea dropper on her just in case, but it’s her legs that’s bothering her, not her ears or head.

Could she have picked up mites?   Has she been to a groomer before and this one?  I'm wondering whether stress might be involved?

I would either give her a bath in something u know suits her.annoyung I know if she has just been groomed  or rather than guessing with treating mites / fleas I would take her to the vet for a check 
I would also tell the groomer when u have a better idea of what it is .

My vet advises that only Piriton is safe for dogs.  Half a tablet would be ok.

I have small dogs too and have used it a couple of times.

If you buy over the counter, just don't tell the chemist it's for a dog because if you do, they won't sell it to you!!  From experience.

Mamabas:

> If you buy over the counter, just don't tell the chemist it's for a dog because if you do, they won't sell it to you!!  From experience

Yip no lies just don't disclose - I do it when I know what has been successful previously.

My vet said pretty much any antihistamine was safe, but I'd stick with the piriton (the original kind only, not Piriteze).

It sounds like she might be reacting to the shampoo.  I'd give the groomer a ring and let them know, so they can use something else next time.  I've had it happen a couple of times with clients' dogs and switching to puppy shampoo stopped it happening again.

If the dog is in a bath the part of them that won't be throughly rinsed will be their lower legs. Also that part of them is most exposed to the shampoo. Sounds like an allergy to me and would make sure that shampoo is not used on your dog again.