Your skin is designed to keep out harmful bacteria which is why it has a slightly more acidic pH than the rest of your body. It however will not perform well if that pH is out of balance.
Here are some tips to balance the pH of your skin.
One way is to steam you face. Pour 4 cups of boiling distilled water into a bowl. Add 1 tbsp honey, 1 tsp apple cider vinegar, and 4 drops lavender oil. Drape towel over your head, keeping face at least 10 inches from water and steam for 10 - 15 minutes.
Use apple cider vinegar as a toner. Mix the vinegar together with distilled water at a ratio of 1:8. Use as a toner after cleansing.
Make a mixture of 1/2 tsp fresh lemon juice with 1/2 cup of water. Rub over face then rinse with tepid water and pat dry.
Avoid using harsh, detergent based soap. These detergents tend to over strip the natural oils and leaves te skin dry.
You can balance your skin's pH from the inside out. Eat a well balanced diet and and eat as much raw food as possible.