It can, and it can't. Using mouthwash is more complicated than you might think, since many common oral rinses used to combat bad breath may also inadvertently cause it. The culprit behind this particular catch-22 is the alcohol found in mouthwash.
Bacteriologically, there is little amiss with using ethanol, or common alcohol, as a solvent or germ-killing rinse. After all, alcohol itself kills microbes, which is a boon for anyone looking to keep their mouth clean.
Unfortunately, alcohol also dries out the palate after use, and a dry mouth is ripe for bacterial growth, which then leads to halitosis. Think of how fast an alcohol-based hand sanitizer dries on your palms. With a much lower boiling point than water, ethanol quickly evaporates, taking moisture with it
Products containing it can desiccate your tongue, leaving it primed for recolonization by bacteria. Studies - like one published in the journal Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology - have also shown that alcohol-based mouthwashes can damage the sensitive tissues of your gums and cheeks if used too often.
Rather than reaching for an ethanol-based mouthwash in the store, consider looking for alcohol-free specialty breath freshening rinses online.