according to this article, herbal treatments and lemon juice seem to be okay. Here's the pertinent excerpt followed by a link to the article:
___________________

Here are a few herbal facial treatments that can be done at home to remove facial hair and slow down re growth. These are effective if done regularly, say every week and require patience and pre testing. Test the mask on the back of the hand for example to check there is no adverse reaction before proceeding.

*

Mix 30 grams of Sugar with 10 ml of freshly squeezed lemon juice in 150 ml of water. Mix well and then apply it on the face in the direction of the hair growth. Leave it on for 15 minutes. Then rinse with cold water, rubbing the facial area gently. The granular Sugar and lemon mixture will act as a gentle exfoliating agent and remove facial hair. The lemon juice will act as an astringent and natural anti septic. Repeat once every week to find an improvement.

Another face mask that can help in reducing hair growth on the face and remove unwanted hair is easy to make and use every week. Squeeze 10 ml lemon juice into 40 ml honey and prepare a mixture. Take a cotton swab and rub this mixture in the direction of the hair growth. Rinse after 15 minutes. Repeat twice a week for 2 weeks and then use it every week to find an improvement in the facial hair condition.
*

An easy to use facial mask to help remove unwanted hair is to squeeze 10 ml lemon juice into a cup of water (150ml). Add 30 grams of Gram flour into this mixture and mix thoroughly. Apply this yellow mixture on the face. Wait for 15 minutes and then scrub your face in the direction of the hair growth to remove unwanted hair.

_________

http://www.janicebeauty.com/facialhair.htm