The person could experience such a condition himself or herself or experience it indirectly, through contact with a sexual partner. For example, a woman who was in contact with a man who ejaculated became unclean along with him. Likewise, a man who was in contact with a woman who menstruated became unclean along with her.
The purification treatments for such conditions never were as complicated as the treatment for leprosy, but they became gradually more complicated and expensive, ultimately requiring the sacrifice of animals at the Temple.
Ejaculation: The Book of Leviticus, Chapter 15, describes the purification for a man who has experienced an ejaculation of semen. He had to wash his entire body with water, but still was not considered to be clean until evening. If the ejaculation happened during sexual intercourse with a woman, then she too had to wash her entire body and was not considered to be clean until evening.
Menstruation: The same Chapter 15 describes the purification treatment for a woman who experienced a menstrual period:
If she gives birth to a girl, for fourteen days she shall be as unclean as at her menstruation, after which she shall spend sixty-six days in becoming purified of her blood.
When the days of her purification for a son or for a daughter are fulfilled, she shall bring to the priest ... a yearling lamb for a holocaust and a pigeon or a turtledove for a sin offering. The priest shall offer them up before the Lord ..., and thus she will be clean again after her flow of blood.
There were several animals that made a person unclean if he ate the animal, but did not make the person unclean if he touched their dead bodies. These were animals that swarm but do not creep -- which included snakes, frogs and scorpions.
The animals that swarm but do not creep can be contrasted to the following animals. Eating the following animals or touching their dead bodies made a person unclean, but touching their live bodies did not make a person unclean.
* Examples of animals that creep are weasels, mice, lizards, tortoises, geckos and chameleons. They walk around on short legs, so that their stomachs sometimes touch the ground, which is creeping.
* Examples of animals that creep and also swarm are rats, mice, lizards, geckos and chameleons. They often move around quickly in groups.
* Examples of animals that creep but do not swarm are weasels and tortoises.
Demons: The above conditions made people unclean because they enabled demons to enter a person's body and then to spread onto or into other persons' bodies. The event of a genital discharge -- an ejaculation of semen, a flow of menstrual blood, the birth of an infant -- opened a person's body and so enabled a demon to enter. After a demon established a base inside one person's body, the demon was more able to move onto another person's body.
Somehow, an animal that creeped -- whose abdomen rose and lowered to touch the ground repeatedly -- was very vulnerable to being entered by demons. Inside such creeping animals, however, the demons were not able to move easily onto people, as long as the animal was alive. As soon as the animal died, however, a demon inside the animal's dead body could move easily into a person who ate or touched the body.
Animals that swarmed -- that moved quickly in a group -- seemed to be possessed by demons. The very act of swarming demonstrated the entire group was possessed. The demons in those animals likewise could not move easily onto people, as long as the animals remained alive. As soon as they died, the demons could move into a person who ate or touched the animal's body.
An animal that does swarm but does not creep -- in particular, a snake -- might be possessed by a demon, but the demon cannot pass through the animal's skin. A person can touch a live snake or a dead snake, and a demon inside the snake's body cannot pass through the snake's skin and move onto or into the person. Only if the person cuts through the skin or cooks the skin and then eats the snake's inside meat can the demon pass into the person.
The purification method for a person who touched the dead body of an unclean animal was to wash the person's clothing, not the person's body. Apparently, a demon inside a dead unclean animal jumped first onto the person's clothing and then had to wait for another opportunity to move from the clothing into the body.
Summary: Some natural, repeating activities of ordinary people -- ejaculations, menstruation, childbirth -- required purification treatments. At the least, the treatments required washing the person's entire body, which still remained unclean until evening. At the most, the treatments required sacrifices of animals at the Temple.
Another common event that required purification treatment was the touching of various dead animals, which were ubiquitous in the environment. In these cases, the person's clothing had to be washed, and the person remained unclean until evening.
A few animals -- in particular, snakes -- could be touched, alive or dead, but they made a person unclean if he ate such an animal. These animals had special skins that contained demons inside the animal's body even after the animal died.