Some people use the homeopathic remedy Rhus Tox with great success for rashes from poison ivy. Some people will never use homeopathy again because Rhus Tox made their rash worse. Some people do in fact need a different remedy, and Rhus Tox can worsen the situation. If you take Rhus Tox and worsen, stop repeating it.
When someone needs Rhus Tox, the rash typically feels worse from cold air and better from hot water.
If the person feels absolutely distraught from the itching, and doesn’t match the Rhus Tox description, it could be that Anacardium Orientale would work better.
If a honey-like fluid is oozing from the area, it could be a case for Graphites. There are other remedies for poison ivy cases of different descriptions.
One of the most effective approaches is to take your “constitutional remedy” for a case of poison ivy, if you know what yours is. (A constitutional remedy matches the person’s overall physical and mental / emotional patterns.) If you are under constitutional care from a homeopath, please consult with them.
One dose of a constitutional remedy in 200c is enough for some people, though it may need to be repeated if itch and rash return. The itch usually lessens significantly within hours with the correct remedy.