For patients on medications that are known to cause photosensitivity, would you counsel them to avoid laser hair removal or laser therapies?  

Depends on which wavelengths the medication is absorbed by.

Has the patient actually had a reaction? How strong was the reaction? A small test area could be performed to see if the patient was sensitive to the laser. Although not a hundred percent guarantee of no reaction, it gives greater comfort with treating.

"Known to cause photosensitivity" is almost every drug, but actually isn't all that common. I Rx doxycycline all summer and maybe see a possible reaction every few years.  Variables are the dose of the drug and the amount and wavelength of light, but mostly studies are lacking. A test spot mi...