In a nutshell, this is actually to be expected when you invert. As a matter of fact, this indicates that the inversion therapy works as it should be. Redness in your face indicates increased blood pressure, therefore, enhanced blood flow to the head – brain, eyes, skin, hair, the whole shebang. Some studies (by Ironman Fitness) show that the brain actually operates 4% faster, as well as twice that in terms of accuracy while you’re inverted. However, these studies are only preliminary, and we should wait for more research before coming to definitive conclusions.
If you do find this feeling to be unpleasant, especially if you are a beginner, it is quite normal and acceptable to take a break. The golden rule of inversion is that you should do it only for as long as you feel comfortable doing it. Moreover, at no point should you exceed half an hour. The minute you feel your eyes bulging from the pressure, you should take a break. This is what the professionals call “intermittent traction”, and it’s a perfectly normal procedure in getting used to inversion and inversion tables.
The fact of the matter is, the more frequently you invert, the more experience you gain, the less you will feel this pressure. If you’re concerned about any possible adverse effects inversion may have on your body, don’t be. It (your body, that is) has mechanisms that are there to prevent damage from hanging upside down, and they are pretty effective.