Lymph is a clear liquid that resembles plasma, but contains a much lower concentration of suspended proteins. It is formed in the plasma during capillary exchange.
Lymph is mainly composed of water, electrolytes, cell waste, and some proteins that leak out of capillaries of the circulation system.
When it leaves the tissue space (interstitium), it travels through the lymphatic vessels to the heart and into the bloodstream. Fluid and dissolved substances are continually being filtered out of the blood.
Approximately 90% of this tissue fluid moves back into the blood capillaries and carried away as part of the venous blood. The other 10% is drained by the lymphatic capillaries that surround the blood capillaries.
Segments of the lymphatic vessels located between the valves contract rhythmically, propelling the lymph along. The rate of these contractions is related to the volume of fluid in the vessel – the more fluid, the more rapid the contractions, and the more rapid the contractions, the more fluid that is able to move.
All this means is that, when a person is dehydrated, there is not enough fluid volume to move throughout the system. When this happens, debris and foreign particles, mainly viruses and bacteria, are able to proliferate because they are not being phagocytized and washed away.