While some bouts of estrus (aka heats) are caused by stress or pheromones from an Alpha, the usual cause is simply the biological clock. A pre-estrus is also known as a precursor to this stage.
Symptoms of Estrus proper include an uptick in nesting habits, confinement of one´s self to the nest, increased slick flow, increased libido, the release of their scent in higher volumes, and sensitivity to scents. For an asexual individual, they will have all of the above symptoms except for an increase in libido.
Treatment for estrus is as simple as letting it run its course. It´s not a condition that yields danger to the individual, though some choose to use suppressants if going into heat proves inconvenient for them. For Omegas in heat, knots are a crucial element. For hetero- or bi-dynamic omegas, a real knot from an alpha will suffice, but homo-dynamic omegas may simply require the use of a heat toy. It is not a cure, but it does make heats easier. Omegas in heat also need to stay hydrated, saturated in the scents of those closest to them, and in their nest. Aside from an asexual individual, Omegas can cut down on the time spent in heat by spending it with their mate.
The first stage is Pre-Estrus. This stage is characterized by increased body temp, cramps, and irritability. Estrus Proper beings after an individual has undergone pre-estrus for three weeks. The actual heat itself is spent in the nest with the mate or partner of the Omega. If the Omega is single, the heat can be spent with someone they choose from a heat share service. During the eight days the omega spends in estrus, they will experience fever-like symptoms and an increase in hormonal functions. The heat itself doesn´t have to be detailed as it is either spent with the mate or in frustration. Heats can be shortened if spent with a mate, but they don´t usually go past eight days.
If a bout of estrus is not suppressed or is unfulfilled, the omega may go feral. Occasionally an omega may experience something akin to nymphomania if a heat isn´t spent with a mate, though asexual omegas do not experience that complication.
Omegas that have begun to go through sexual maturity are the affected group, though Betas past sexual maturity will go into estrus in a population with a majority of Alphas.
Omegas can deter estrus by taking suppressant pills.
Only Omegas experience heats in the fashion I described, though Betas will experience heats if there is a surplus of Alphas in their population. Some Omegas aren´t affected by heats due to hormone imbalances. Heats also can change course if they are linked to a traumatic event in an Omega´s life. For instance, their scents may change to that of an aggressive Alpha´s, deterring or agitating Alphas instead of attracting them. Heats also take the form of ruts for them and they display more aggression and territorial behavior than others. Heats for full-orcs only come for a three-month period while half-orcs endure them every month.
No significant history. Omegas have been having heats since the beginning of time, though there have been some Omega-only societies that create rituals around heats.
Omegas in heat are taken care of in any culture. There are some cultures that perceive Omegas in estrus as weak, but most view them as desirable and attractive.