Is the fast of one who bled from a tooth and swallowed the blood while trying to expel it valid?

If blood exits the mouth and is swallowed unintentionally (due to an overwhelming urge or forgetfulness), the fast remains valid and there is no need for a make-up fast. This is analogous to the principle that vomiting does not invalidate the fast if it is overwhelming, and that eating and drinking out of forgetfulness do not invalidate it.