As with all cosmetics there's always a chance that you might have some sort of reaction to a particular ingredient. Please observe the following guidelines:-
Sensitive skin - always do a skin test first. Put 2 drops of essential oil in 5 ml of carrier oil and test on upper arm.
Pregnancy - now I realise that the chances of any men out there getting pregnant is negligible but you may decide to use it on your partner. If you do I recommend you don't use essential oils for the first 4 months and after that many oils can be quite beneficial in half dilutions.
High blood pressure - avoid rosemary
Epilepsy - avoid basil,eucalyptus and fennal, use rosemary sparingly
Diabetes - Avoid eucalyptus, geranium and lemon
Sunburn - avoid bergamot, citronella, grapefruit, lemon, lime, orange, manderin, tangerine amd all other citrus oils you may come across
Whilst drinking alcohol - avoid clary sage
Nut allergies - avoid all nut oils
With all products - Never exceed recommended dose, do not take internally, all oils when applied to skin should be diluted with a carrier oil with the only exceptions being Tea Tree, Lavender and Chamomile (TLC), alternate oils regularly for recurring conditions, if you use the same oil too often your body becomes accustomed to it making it less effective, if using prescription drugs always seek medical advice before using essential oils.