Hi , I'm James DVM MRCVS and would like to help you with your question
Sorry to hear about Toby but I believe I can help.
Westys are notorious for suffering from skin conditions and having sensitive skin which is very susceptible to development of allergies
One of the most probable things is that Toby is suffering from what is called Atopy - mean an allergic reaction to something in the environment like pollen , grass , certain types of insects even and the list goes on and on.
This is why you found these small raised patches which symbolizes a conditions called urticaria (hives) .
some special shampoos might help relief the symptoms just mildly but usually what's needed is medicinal help in order to stop the cycle of itching plus minimize exposure to the elements which might have caused it in the beginning , so here is what I want you to do in order to help Toby.
1. But a drug called Piriton (DO NOT buy any other drug against allergies even if offered by the pharmacist as they are not approved for dog use) . choose the one which tables are 4mg or 8mg in dose . Give Toby 4mg (either one tablet of 4mg or half of 8mg) tablet every 8 hours for the upcoming 24h . If signs improve and Toby is not too sleepy while he is with you , then you can continue till his owner returns. if he is still litchi then give 8mg - 4mg -4mg , if still no improvement then 8mg-8mg-4mg . by that point is should have made a difference
As I mentioned , Piriton may make him sleepy so don't be alarmed but as well , try to reduce the dose if he is too flat .
2. avoid wooded areas and parks for the time being and walk him on asphalt roads .
3. When his owners are back , let them know of the situation and advise them to see a vet to have a blood test done which can help diagnose what is Toby allergic to.
I hope this help.
Please let me know if you have further questions.
all the best.