It can certainly reduce stress and anxiety. It can reduce allergies as well if what you mean by healthy eating means reducing the intake of pro-inflammatory foods that can cause or exacerbate allergies. The most common of these for most people is dairy and wheat, but soy and corn can also be common problems. Eating organically grown foods might help, as they might have fewer chemicals on them that you might be allergic to or that might force your immune system to go on overdrive. Too much sugar also can cause inflammation. But a lot of it depends on what you're allergic to and why. Allergies are an auto-immune disorder, in the sense that the things we're allergic to aren't in fact bad for us most of the time but our immune systems are attacking them anyway. Tamping down the immune system helps reduce allergy symptoms. Some things that can cause the immune system to become overactive are other auto-immune disorders, second-hand smoke (or first-hand), over-exposure to toxic chemicals in the environment, eating foods your body doesn't tolerate well, use of antibiotics, etc. Anxiety makes us perceive everything as worse than it would be otherwise quite often, but it doesn't "cause" allergies, but anxiety is sometimes caused by physiological problems that can also cause immune systems to go haywire and make us react to things in an allergic way. Exercise can also help by speeding up the body's evacuation of things that bother it. But if you have allergies and go to the gym, please be careful of the current fad of using tons of germ killers -- they are not only toxic in themselves, but are like using antibiotics, killing off beneficial bacteria that are part of our immune systems and causing them to become overactive -- not to mention creating antibiotic resistant bacteria.