1 - Water Solubility - Type the name of your treatment and "water solubility" in a Google search. Your treatment needs a solubility between 35% to 100% to penetrate the nail to treat your infection. For example, tea tree oil is 15% water soluble, undecylenic acid and Ketoconazole are less than 1% water soluble. - none of which are likely to penetrate the nail in high enough concentration to cure the infection.
2 - Energy - Type the name of your treatment and "maximum storage temperature" in a Google search (or check the packaging). If the maximum temperature is greater than 37° C (body temperature) then the medication has the additional energy to penetrate the nail. For example, Penlac has a maximum storage temperature of 30° C.
3 - Nail Thickness - Type the name of your treatment and "ingredients" in a Google search (or check the packaging). If the ingredients includes nail thinners such as papain, salicylic acid or urea the treatment thins the nail for better penetration.
4 - Modes of Action - Type the name of your treatment and "modes of action" in a Google search. If the number of modes is greater than two, the treatment is more likely to cure your infection. For example, clotrimazole, miconazole and tolnaftate all have only one mode of action.
5 - Electrostatic Repulsion - Type the ingredients from your medication individually into a Google search. If the description of the ingredients includes the word "surfactant" then your medication will neutralize the repulsion between the nail and the medication for better penetration.
6 - Powerful Antifungal - Type the name of your treatment and "MIC" in a Google Scholar search. The lower the MIC value the smaller the treatment concentration necessary to cure the infection. For example, undecylenic acid has an MIC of 60, tea tree oil's MIC is about 800 and for ketoconazole it's MIC is 0.22.