(Will update if possible)
The letters of אייר stand for many different things. Here are a few:
(ליקותי מוהר׳ן) אֹ׳יְבָי יָ׳שֻׁבו י׳ֵבֹשׁוּ רָ׳גַע - Interestingly enough Reb Nachman connects this posuk, from Tehilim 6, with a posuk from Tehilim 67, which is connected to Sefiras HaOmer.
Since Iyar is associated with healing we will list some segulas for refuah, in addition to other segulas associated with sefiras haomer.
Reb Pinchos of Koritz says that he rains that falls between Pesach and Shevuos is a great refuah for diseases that have no cure, rachmana litzlon. 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). We are not sure whether he means one should swallow the water or not.
The following is from Breslov Weekday Customs (P.62):
The Rebbe states that in "Vayevarekh Dovid," when one recites the phrase "u-tzeva'ahhashomayim Lekha mishtachavim . . . The heavenly hosts prostrate themselves unto You" (Nechemiah 9:6), it is a favorable time for one to add a personal prayer. According to Kitzur Likkutei Moharan I, 231: "[At this moment] one may pray for everything, for then all the angels prostrate themselves and render homage to G-d, may He be blessed. Therefore, it is good to entreat that HaShem command them to transmit whatever one needs. For example, if one needs healing, one should meditate that HaShem command [the angels] to invest the spiritual powers of healing into one's bread and water, etc."