I remember that a few years ago, it was raining in Iyar and someone (who I believe to be a talmid chacham) told me that drinking the rain in Iyar is a powerful segulah for refuahs. Today, Rosh Chodesh Iyar, it rained quite a bit. I remembered this, and now I have 2 questions. A) Does anyone know a source for this? B) The mishna in Mesechta Taanis refers to rain in Iyar as a siman klala. How do we reconcile the two facts(assuming the segula does exist)?
Possible answer: The Sefer Ta’amei HaMinhagim asks why is Iyar a time of healing? He sources the Bnei Yissaschar who teaches that most weakness and illness come from foods which do not comport with a person's nature or composition. Since the Manna began to fall during this month (on the 15th day of Iyar 2448) - and it was a perfect food from which resulted no sickness, pain or even waste matter and even cured those who were ill - Hashem left the curative nature of the month in effect even through today. Accordingly, Iyar is a time of healing.
Reb Pinchas of Koritz says that the rain that falls between Pesach and Shavuot is a refuah for diseases that have no cure. One should let the rain fall on their head and open their mouth to let the rain go straight in (some places say to the right side of the mouth).
Reb Pinchos of Koritz one of the talmidim of the Baal Shem Tov is said to bring it down that the rain that falls between Pesach and Shavuos is a refuah for diseases that have no cure r"l. One should let the rain fall on their head and open their mouth to let the rain go straight in - I don't know the exact source though.
the segula is attributed to Rebbi Pinchas of Koritz, as has been mentioned.
There's an additional point about Iyyar. איר is roshei teivos אני י רופאך the pasuk "I am Hashem your Healer." This is also mentioned as an additional maaleh of refuah in Iyar in general.
(I saw it years ago in a collection of dvrei torah from the Chasam Sofer, but I don't know where. Someone today told me the Lubavitcher rebbe discusses it in a sicha, but he didn't know either.)
I don't think this has to contradict the Mishna in Taanis. Rain during this time is a siman klala; it's not beneficial for the crops, which need to be drying at this point. The fact that the rain is not wanted now doesn't mean it can't have healing properties (especially based on the segula of the month in general.)