הלכות טומאת צרעת

The following principles apply with regard to a person who had a wound on the flesh of his skin and the skin peeled away because of the wound. If the wound came about because of fire, e.g., he was burnt by a coal, embers, iron or stone that were heated in fire, or the like, it is called michveh, a burn. If the wound did not come about because of fire, e.g., he received a blister from stone, wood, or the like, or the wound came about because of an infirmity within the body, a wart or eczema that ruined the skin or swelling lesions, feverous swellings, or infections that ruin the skin, it is called sh'chin, a boil.

The following laws apply if one heated a spit and hit another person with it. If its end was rounded, the wound it produces is considered as a burn. If its end was pointed, there is an unresolved question if it is considered as a burn or a boil.
When a person suffers a burn because of the hot springs of Tiberias, olive dregs, or the like, the affliction is considered as a boil.

As long as boils and burns are fresh, festering wounds, they are called mordin and do not impart impurity because of tzara'at at all. If a boil or a burn heals and the afflicted person's flesh was entirely restored - even though there is a scar on the place and it is not entirely like other skin - it is considered like ordinary skin with regard to all matters. Such a person is deemed impure because of the three signs mentioned above and he is isolated for two weeks as part of the process of determination as explained.

If the boil or the burn began to heal and be restored, with a scab like the thickness of a garlic peel forming over them, this is the "scarring of the boil" mentioned in the Torah and the "healing burn" mentioned there. They impart impurity because of two signs: white hair or an increase in the size of the blemish and such a blemish is isolated only for one week.
What is implied? There was a baheret on the scarring of a boil or the healing of a burn. If it contained two white hairs, the person should be deemed definitively impure. If it does not contain white hair, he should be isolated for a week and examined at the end of the week. If white hair grew or size of the blemish increased, he should be deemed definitively impure. If there was no new development, he should be released from the inspection process. If size of the blemish increased or white hair grew after he was released from the inspection process, he should be deemed definitively impure.

A healing boil and a healing burn cannot be combined with each other. For that reason, the Torah described them separately, to teach that they are not to be combined, nor can they expand into each other, They do not expand into ordinary flesh and a baheret that is on ordinary flesh does not expand into them.
What is implied? If there is a boil next to a burn and a baheret that comprises a gris extending over both of them, the person is pure. If a baheret was in either of them and it extended into the other or it extended into ordinary skin, he is pure. If there was a baheret on ordinary skin and it extended to one of these, it is not considered as an extension.
When a person had a healed boil that was the size of a gris with a baheret the size of a gris on the palm of his hand, he should nevertheless be isolated. Although it is not fit to grow white hair, nor to expand, there is the possibility that he will develop another boil next to it and the baheret will spread into it.

When a boil became a burn, the burn nullifies the boil. When a burn became a boil, the boil nullifies the burn. If it is not known whether a blemish was a boil or a burn, it is not significant, for they both contract impurity due to the same signs and the impurity is the same. Scripture differentiates between them only to teach that they are not to be combined.

If a person was isolated because of a baheret in a boil and at the end of the week, the boil healed and became ordinary flesh or he was isolated because of a baheret on ordinary flesh and at the end of the week, it became a boil, he should be given an initial examination.

When all the hair on a person's head falls off, whether due to sickness, due to a wound that makes him unfit to grow hair, or due to eating foods that cause hair to fall off or applied lotions that cause hair to fall off, since he lost all of his hair at this particular moment, he is called a keireiach or a gibeiach, even though he is fit to grow hair at a later time.
If his hair from the top of his forehead and downward, descending backward until the first vertebra of his neck falls off, he is called a keireiach. If his hair from the top of his forehead and downward, descending frontward until it is level with his forehead falls off, he is called a gibeiach.

With regard to both of these types of baldness, a person can contract impurity when a baheret appears on the skin through two signs: healthy skin and an increase in size. They should be isolated for two weeks, for Leviticus 13:43 states: "Like the appearance of tzara'at on the flesh of the skin." Since these portions of the body do not grow hair, the appearance of white hair is not a sign of impurity for them.
What is meant by incurring impurity through either of two signs and that a person may be isolated for two weeks. If there was a baheret in a bald spot whether at the back of a person's head or at its front and there was healthy flesh in it, he should be deemed definitively impure. If it does not have healthy flesh in it, he should be isolated and examined after the end of one week. If healthy flesh appeared or the blemish increased in size, he should be deemed definitively impure. If nothing changed, he should be isolated for a second week. If the blemish increased in size or healthy flesh appeared, he should be deemed definitively impure. If nothing changed, he should be released from the inspection process. If the blemish increased in size or healthy flesh appeared after he was released from the inspection process, he should be deemed definitively impure.

These two forms of baldness are not combined with each other, as indicated by Leviticus 13:42, which makes a distinction, stating: "on his karachet or on his gabachet." This teaches that they are two types of conditions and blemishes do not spread from one to the other, from either of them to ordinary flesh, or from ordinary flesh to them.

When there is a boil or a burn on a karachet, on a gabachet, or on a beard that has lost its hair, they are deemed impure in the same way as is a boil or a burn on ordinary flesh. For when one loses the hair of his head or of his beard, these parts of the body are considered as ordinary flesh with regard to all matters except that they do not contract impurity because of the emergence of white hair.
When hair has never grown on one's head or on one's chin or when there is a blister on one's head or chin, the surface is considered as ordinary flesh and they are deemed impure because of three signs and requires isolation for two weeks. Similar laws also apply to the chin of a woman and a sexually inadequate male. Until hair grows on these surfaces, they are considered as ordinary flesh. If they grew hair, they are considered as the chin of a male and incur impurity as a netek does, as will be explained. They do not incur impurity because of a baheret.