The etrog is a citrus fruit; its appearance is beautiful, its aroma pleasant and its flavor delicate. The Torah refers to it as “The Fruit of the Majestic Tree”, and in the literature of our sages it is compared to the human heart.
The etrog is one of the four species that we hold on Sukkot when fulfilling the commandment. There are very important medicinal properties in the etrog; some are natural and some mystical. Some of its mystical features include: Looking at an etrog for eye disorders. A barren woman should eat an etrog on the festival of Hoshana Rabbah, but it should specifically be an etrog that had the blessing of the four species recited on it. A person who spends a lot of money on his etrog for the sake of Heaven and not to show off, will have sons who are occupied in the study of Torah.
It is customary to make jam out of an etrog that was blessed and eat it on Tu B’Shvat.
As for its natural properties: A person who has a speech impediment should chew on the peel of an etrog. Eating the peel of an etrog strengthens the heart. The etrog balances the function of the liver, increases appetite and invigorates. Anyone suffering from depression should eat this fruit. The juice of an etrog helps quench intense thirst and stabilizes blood pressure. One should not eat an etrog in the middle of a meal or after it, rather, in-between or before meals. In addition, it is important to note that the peel of an etrog is hard to digest, so anyone suffering from digestive problems should avoid eating it.
Rubbing the flesh of the etrog on stains will make them completely disappear.
And finally, the scent of the etrog will ward off moths from your wardrobe.