Avoid exposure to substances that can set off an allergy attack.
But researchers are looking for other substances that can help the immune system develop properly.
("Precursors" are substances that can aid the production of chemical weapons, and may themselves be harmful).
Carcinogens are substances that can lead to cancer under certain levels of exposure.
There are some substances that can be controlled, like the reagents used to modify DNA.
Since then, they have started using a variety of other injectable substances that can flatten or fill lines and furrows.
Grapefruit juice contains unique substances that can block the breakdown of some drugs, thereby affecting their absorption and effectiveness.
Ibuprofen and similar drugs may raise blood pressure by blocking production of prostaglandins, hormone-like substances that can widen blood vessels and improve blood flow.
But we are not dealing here with the distinction between separate substances that can be conceived to exist independently from one another.
Chocolate is a rich source of antioxidants, the substances that can block cellular and arterial damage caused by oxidation reactions that go on endlessly in the body.
While some players get the desired result from amphetamines, others use legal substances that can be found in over-the-counter supplements.
