Essential Lavender

yes completly safe. Maybe duluty it with a little almon if you wish but it don’t hurt him if you know he is not allergic.
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You should bring the boy to see a doctor to get it laser off as they can be contagious. Although lavender oil has healing properties, the spread of warts will still persist as it’s cause by the contagious HPV, the same kind that causes genital warts. Lavender is more known to be antiseptic and anti-bacterial. To temporarily treat the problem, apply Tea Tree oil neat (soak a cotten-bud with it) on the warts and nowhere else. Tea Tree oil is highly anti-viral. Please not that this is a temporary measure so do get the boy to see a doctor asap.
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Essential oil sales-girl with aromatherapy knowledge.

Lavender and tea-tree are usually the essential oils that are safe to put directly on the skin, but I wouldn’t use lavender for molluscum - which is contagious and can spread over the rest of the body and sometimes can become infected. It is not dangerous. But you should take him to see a homeopath in order to distinguish the growths i.e. whether they are warts or molluscum and an appropriate treatment needs to be given.
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Encylopedia of Aromatherapy oils
Personal experience with a 4 year old

Lavender oil can be applied neat (without carrier oil) but for the warts use some Oil of Oregano to clear them up.

/Lamar
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yes safe
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Beautiful and useful! Well done!