It seems that your wife may be having urticaria.
Nettle may be responsible for urticaria.
There may wheal with severe itching
and burning pain.
Give her antihistaminic like levocetirizine
If needed, steroids may be given in tappering dose.
Calamine lotion may be applied to soothe the skin.
Avoid soap bath.
If poor response, consult dermatologist
for thorough investigation.
I hope you got my answer.
Dr. Ilyas Patel MD