The yellow phlegm may be due to a bacterial infection, but if your coughing is due to asthma, I have relied on Tilade (now) and Intal (earlier) to quell my coughing due to asthma. Tilade and Intal, as MDI (medicated dose inhalers), are no longer for sale in the U.S. (manufacturing issue -- http://www.in-pharmatechnologist.com/Industry-Drivers/Inyx-drama-highlights-crucial-need-for-due-diligence-on-contractors), so I get Tilade inhalers (which I consider more effective than Intal inhalers) from Inhouse Pharmacy (http://www.inhousepharmacy.biz/asthma-allergy/tilade.html). Intal inhalers are probably available from a Canadian or a U.K. pharmacy. (I don't mean to be a shill for Inhouse Pharmacy, but I find it is the cheapest place to get Tilade inhalers, and is very reliable, as well.)
Alternatively, if you have a nebulizer, you can still get cromolyn sodium (Intal) inhalation solution in the U.S. from Teva Pharmaceuticals (http://www.tevausa.com/default.aspx?brandName=Intal%C2%AE%20Inhalation%20Solution&pageId=76), but I find Tilade inhalers to be the most effective of the 3 alternatives I've mentioned. (The cromolyn sodium inhalation solution may be the cheapest, however, since it is a generic.)
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