Definitely do a patch test on your skin first, even if you've never had an allergic reaction before. Can you use a semi-permanent dye? They say only a small amount of the chemicals are absorbed through your skin. From APO (link below): "Permanent hair dyes contain ammonia which has a strong chemical fume. The recommendation is to avoid hair dyes that contain ammonia. "
This is from the American Pregnancy Org: "Are hair dyes safe during pregnancy?
According to the American College of Obstetricians and Gynecologists (ACOG), hair dyes are probably safe to use during pregnancy because so little dye is absorbed through the skin. However, it is still important to be cautious, therefore many health care providers recommend that pregnant women not use permanent hair dyes during the first three months.
While the absorption through the skin is minimal, the concern is that breathing fumes during the process could be harmful to the developing baby. Permanent hair dyes contain ammonia which has a strong chemical fume. The recommendation is to avoid hair dyes that contain ammonia. The chemical fume warning also applies to straightening products as well."
Personally, I would be fine with it, but I would follow the above guidelines--if you read the page, these are the safety tips:
"Consider waiting until the second trimester for hair dye, bleaching, permanents or straightening.
Have the treatment completed in a well-ventilated area.
Dont leave the chemicals on your head any longer than necessary.
Rinse your scalp thoroughly with water after treatment.
Wear gloves when applying chemicals.
Carefully follow directions on the product package.
Do a patch test for allergic reactions before completing the process
Never dye or bleach eyebrows or eyelashes. This could cause swelling or increase risk of infection in the eye area."