This looks very much like an allergy. It is probable that she has developed an allergy to something, you should check out whether you have started any new soap, ointment or detergent within this period. It could be from some new article of clothing or jewellery. They might also be due to some new medications that she is using.
It could also be due to some food that she took very recently. Watch out for foods like shell fish, sea fish, meats, cheese, etc. Also any new types of processed foods. If you do find anything which could be the cause, then try to avoid it.
Another possibility is bug bites like bed bugs, mosquitoes, spiders, etc. In any case the treatment would be the same.
Next, she can take an anti-allergic medicine, an antihistamine. But for any use of antihistaminic before 2 years of age, you should first discuss with her doctor, give her only after discussing with her doctor. She can take Benadryl elixir for children, an OTC anti-allergic medicine. The dose is about 0.5 mg per pound of bodyweight (or 1.25 mg per kilogram). For example, a 25 lb child would get one teaspoon of liquid or one chewable tablet every four to six hours.. However you should also talk to her doctor before giving an antihistamic below 2 years. Also, apply a soothing lotion like calamine lotion, also available OTC.