Thanks for your quick feedback!
You have two options: Benadryl, which may work faster but lasts less time so you have to give it 3-4 times a day, and may have side effects more often, such as drowsiness, or stimulation in very young children.
Second choice: Reactin: It may be a little slower acting, but it only has to be given once a day, and is usually very well tolerated
I suggest you visit your pharmacist, he/she can show you which one you choose according to your preferences, and will indicate the volume to give him/her according to his/her weight.
Also, I strongly suggest applying a fragrance-free moisturizer such as Aveeno or Base Glaxal, as often as necessary. You will have to monitor the situation to make sure that it tends to diminish, which should be the case if it is an allergy and if the exposure to the allergen is stopped.
I hope I've been helpful, so please don't hesitate if you have any other questions!
Tom Samaha, pharmacist