How long do your allergies last? My guess would be that if you needed to take decongestants for a couple weeks, it would not hurt your colostrum at all by the time baby arrives, even if he/she is a little early. I'd ask your ob/midwife about it just to be sure though.
DH married for 12 years, parents to 7 small people
Five of these:
and two of these:
including our newest addition, born 26-08-13