According to MSDSes at Freestyle, LPD contains hydroquinone. Although hydroquinone has not, to the best of my knowledge, caused anybody to grow a third arm or anything, my understanding is that it is nastier than ascorbates/vitamin C. For the absolute best safety when children (and safety-conscious parents) are concerned, IMHO it's better to go for a PC developer than anything with hydroquinone in it. The LPD MSDS doesn't mention either phenidone or metol, so I don't know if it contains either of those chemicals. (MSDSes sometimes omit chemicals that are used in small enough quantities. Phenidone in particular is used in very small quantities in developers, so it's sometimes not mentioned.)