A researcher says the effectiveness of cold and flu medicine has always been dubious

Firm JGA Saddler's filed a law suit against pharma giant Johnson-and-Johnson in the High Court, accusing it of misleading customers.

The US Food and Drug Administration's ruled a key ingredient in Codral, Sudafed and Benadryl cold and flu products, is ineffective when taken orally.

Waikato University School of Pharmacy and Biomedical Sciences' Professor Rhiannon Braund says even without medicine, colds will eventually go away.

She says all we can ever do is make ourselves feel better, like cough lozenges only help because of their syrupy nature.