If a plate with oceanic lithosphere meets another plate, the dense oceanic lithosphere dives beneath the other plate and sinks into the mantle: this process is called subduction. The sinking oceanic lithosphere drags the rest of the tectonic plate: this is the main cause of plate motion.
You may notice a decrease in symptoms during the build-up phase, but it may take as long as 12 months on the maintenance dose to notice an improvement. If allergy shots are successful, maintenance treatment is generally continued for three to five years.
A year's supply of allergy shots can run between $800-$1,000 for the first year, and may be even less if you have a solid medical insurance plan with a decent co-pay. Although you may need to take shots for between three and five years for optimal effect, this may still be cheaper than over the counter alternatives.