Your question is not very clear when you mention 'skin allergy' over 20-25 years. If what you are referring is itchy red weals all over the body with or without swelling of lips/tongue for so many years, it is quite a common condition called urticaria
. If there no obvious triggers, like commonly used pain killers (ibuprofen
, codeine-based analgesics) or allergy to pollens etc then the condition is idiopathic (meaning all known causes excluded) and responds to long-term high-dose non-sedating antihistamines.
or hormone abnormalities or stress can prolong the symptoms, but infection triggers are also common. So infections need to treated and high-dose antihistamines must be used at the same time. Your doctor has rightly given you a short course of steroids
which is sometimes the last option. Cetirizine
10mg twice daily or allegra 180mg (morning) and 90mg (at night) plus or minus atarax 25-50mg at night are the usual treatment options. Must be used for 3 months at least without any attacks.
Also rarely, patch skin tests are done to exclude chemical triggers.
I hope this will be useful.