Can I taper 40 mg to 10 mg Prednisone after 5 days for Poison Ivy

I have been prescribed 40 mg for 7 days. I took that for 5 days, rash is way better, basically gone. Slight red skin where it was. I felt awful last night (headache) and weird/shaky this morning. I took 10 mg (day 6) this morning instead of 40. Will that still keep the poison ivy from rebounding? Thank you