Citronella Rollerball is made using essential oils and can be applied to the skin after a bite. Uses essential oils of Citronella. Volume: 10ml Aromatherapy rollerballs are made with pure essential oils diluted in carrier oils. Aromatherapy rollerballs are great to use. Just pop any of these aromatherapy rollerballs into your handbag, pocket or keep it under the pillow for instant use.