Hi the safety information on Lemon Oil is that it is non toxic but may cause dermal irritation or sensitization and is to be used in low doses.
If the skin has become sensitized it will be more sensitive to the same irritant in the future, when it may cause a rash, blotches, itching or blistering even if very dilute. Care should be taken with Geranium, Ginger, Pine, Juniper, LEMONGRASS and a patch test before using any essential oil in the future would be recommended.
Aroma Amethyst