Thanks for writing your query.
You should wash the affected area thoroughly.
is a decongestant and will not be helpful in controlling the allergic reaction
You should take antihistaminic medicine like Fenofexadine
Application of Calamine lotion will help in decreasing the itching sensation, but local application of steroid cream will be more beneficial.
You should get yourself examined clinically at the Emergency Department and take the appropiate medicine.
Donot apply the post-wax treatment oil in future, as your skin is sensitive to it.
I hope this is helpful to you.