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CORNS
QUESTION: I was recently inquiring about cures for corns when i came upon tagete oil in
a book of mine. Perhaps my book is vague, as it does not warn me of the
hazards of this oil. As I cannot find any other way around this corn, and it does need
to go, I'm considering using the tagete oil. Do you have any particular cautions?

ANSWER: 
I am not an Aromatherapist and have not had their training, what I know about Tagetes oil is:

Here are 3 commercially available Tagete oils each are made from a different plant species

TAGETES GLANDULIFERA grows wild in south Africa, East Africa and Nigeria.
from Mexico

TAGETES MINUTA from EGYPT

TAGETES PATULA from INDIA

Other Tagetes species include

Latin Name Common Name
Tagetes erecta African Marigold

Tagetes lucida Mexican Marigold,
Mexican Mint Marigold
Mexican Tarragon
Sweet Marigold
Winter Tarragon

Tagetes tenuifolia Lemon Gem Marigold
Lemon Mint Marigold
Lemon Marigold

Tagetes filifolia Irish Lace Marigold

Tagetes minuta Mexican Marigold

Tagetes patula French Marigold

Tagetes signata

For the Tagete essential oil the plants common name is normally Marigold.

The warning for these essential oils is they all have phototoxic effects. 

When fresh, the essential oil is golden yellow with a fruity smell, some describe it as apple. As the oil ages and is exposed to oxygen it becomes harder and solidifies like a resin.

For more ideas on removing your corn read my other answer for Warts under Skin Conditions for herbs which are ESCHAROTIC, flesh eating, such as Bloodroot.