Certain Dri Anti-Perspirant is available with 12 percent aluminum chloride the active ingredient used in prescription anti-perspirants. Because Certain Dri is water-based (vs. alcohol-based like its prescription competitors) it is available without a doctor s prescription. This doctor-recommended non-prescription product is applied several times a week at bedtime. According to an independent survey a majority of dermatologists prefer the Certain Dri formula for treating hyperhidrosis or excessive perspiration over the formula in all the other anti-perspirants combined.