It was my first impulse when I read medicine to the eye and the heart
Atropine or the plant that derives it, Belladonna (Also known as deadly nightshade)
Hear me out.
I am what they cherish,
Those who cherish,
Are also those who detest ardently.
I murder with ease and comfort,
Atropine is a potent toxin in high doses
And be loved with purpose.
in medicinal doses it is an important medicine, it's on the WHO Model list of essential medicines
I am a drug to the eye,
It was, tho not so much anymore, used for pupil dilation in ophthalmology.
And to the heart,
It is also a treatment for bradycardia (Dangerously low heartrate)
You love me like nobody else,
Not because I murdered your loved ones,
But because I am a drug to the eye,
Belladonna at a recreational dose is a hallucinogenic. It can be consumed by squeezing the berries into your eye.
and to the heart.
It has been used in the past as a cosmetic (love/attraction),
I cause no disease,
but yet I abolish those who you love,
but it's still poisonous, and may kill those using it haphazardly as a cosmetic.
For I am a drug to the eye,
and to the heart!
lost loved (and beautiful) ones.
As for the hints, this is definitely a physical thing, and (plants in the family producing it) can be found everywhere (except Antarctica)
As a warning to anyone who may not have been aware of this before, the experience recreationally is usually reported as unpleasant, and the difference between a recreational dose and a fatal dose is scary close. Don't be an idiot.