It may be the mandarin oil, or the wheatgerm; I would use a different carrier; usually wheatgerm oil is used 10 % in a mix of other oils. Coconut oil (extra virgin) Almond or olive oil + 10 % wheatgerm oil.
Coconut oil is the best!
I used aromatherapy a lot when pregnant; no stretchmarks was one of the outcomes.
Lavender is the safest oil of all Mandarin oil gave me a rash when I used it; it may have been contaminated.