Probiotics were recommended to me by my doctor to be taken every day regardless of antibiotic use or not --to boost my immune sytem. I balked at first saying I always took a 3 strain acidophilus and it did nothing for me. She told me to take the 10-15 strain probiotic -- and that did actually help stop the candida overgrowth. I'm not on antibiotics, but I wonder if years of continually being on them messed with the balance of the good/bad bacteria. Also for me -- the inhaled steroids is something else that makes yeast overgrowth possible.
My doctor recommended pharmaceutical grade or at least standardized supplements because it has been reported that over half of these products do not have what is stated on the label in substance or amount, and in some cases the purity is very questionable...
To be honest I don't take the pharmaceutical grade or the best standardized probiotic which is why once in a blue moon I get thrush in the back of my throat (again due to the inhaled steroid) Then I switch to the better product.