Thank you for your medical query at AskTheDoctor.com
I understand your concern.
Benadryl won't really help with the itching especially if it is Scarlett fever.
Rather an antihistaminic like Levocetirizine would have been more helpful.
I will advise you Tab. Loratadine, which is better compared to both Benadryl and levocetirizine, and will reduce the itching.
Hope this was helpful,
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