The Mangekyō Sharingan — drains a considerable amount of chakra and strains both the user's eyes and body, a drawback which affects a non-Uchiha even more so. Use of the dōjutsu gradually deteriorates the user's eyesight to the point of blindness.
Creation Rebirth ( Sōzō Saisei) — By releasing the great volume of chakra stored in her forehead at once, the body's cell division is forcibly stimulated by proteins, reconstructing all organs and all tissues making up the human body. The technique itself does not regenerate the old cells, rather it hastens the creation of new ones through division. If this technique is used, a body whose vital organs are so gravely injured that it cannot bear it any longer will be instantly restored to its uninjured state.
Strength of a Hundred Technique (Ninpō Sōzō Saisei) — similar in nature to its parent technique, which also regenerates the user's wounds via accelerated cell division, the Strength of a Hundred Technique has a continuous, automatic effect that will heal any damage that the user sustains instantly without the need to make hand seals or even a conscious effort to activate the healing process as long as they have chakra left.
Considering the datebook info provided above The Byakugō Seal (Creation Rebirth/Regernation) should be able to negate the side effects of The Mangekyō Sharingan due to it's healing properties.
Creation Rebirth ( Sōzō Saisei) — By releasing the great volume of chakra stored in her forehead at once, the body's cell division is forcibly stimulated by proteins, reconstructing all organs and all tissues making up the human body. The technique itself does not regenerate the old cells, rather it hastens the creation of new ones through division. If this technique is used, a body whose vital organs are so gravely injured that it cannot bear it any longer will be instantly restored to its uninjured state.
Strength of a Hundred Technique (Ninpō Sōzō Saisei) — similar in nature to its parent technique, which also regenerates the user's wounds via accelerated cell division, the Strength of a Hundred Technique has a continuous, automatic effect that will heal any damage that the user sustains instantly without the need to make hand seals or even a conscious effort to activate the healing process as long as they have chakra left.
Considering the datebook info provided above The Byakugō Seal (Creation Rebirth/Regernation) should be able to negate the side effects of The Mangekyō Sharingan due to it's healing properties.