It is sometimes claimed that the multiple personalities of a person with dissociative identity disorder may not only display different character, behaviour, and movement types, but even show different functionings of the body. Quoting,

One example is a boy who endures allergic reactions when drinking orange juice including symptoms such as hives and water filled blisters which subside immediately when he switches to a different personality.

Another mention of (probably) the same case is here. So to be concrete: Is this particular story correct?

In general: Have there been verified cases of split personalities with significant differences in body function, such as a different immune system, different hormone levels or different physical strength?

While my first link provides some references to publications on this topic, I am uncertain as to whether they represent the scientific consensus, in particular in light of the controversy on split personalities mentioned at this related (and still unanswered) question.

This question was inspired by the movie Split, where this is a major theme.

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    If nobody on this site is able to answer if multiple personalities even exist, how would someone be able to answer the title question?
    – paradisi
    Jul 1, 2017 at 0:45
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    A related question: Did a nocebo study find that rashes could swap hands?
    – paradisi
    Jul 1, 2017 at 0:46
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    @sumelic: Mainly by providing a negative answer to this question without arguing against the existence of multiple personalities as such. But even a positive answer to this question may not presuppose a positive answer to the other one: different personalities may display different physical traits even if DID is merely therapy-induced.
    – Saibot
    Jul 1, 2017 at 1:19
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    Closely related: skeptics.stackexchange.com/questions/6766/…
    – Oddthinking
    Jul 1, 2017 at 5:13
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    The journal article "Dissociative identity disorder and ambivalence" Philosophical Explorations, volume 19, page 223, doi.org/10.1080/13869795.2016.1199728 says "there is some evidence that they may even have different allergies", but I don't have easy access to the full text.
    – DavePhD
    Sep 30, 2019 at 11:58

1 Answer 1


According to The Phenomenon of Dissociation, Australian Institute of Professional Counsellors :

The phrase “dissociative identity disorder” replaced “multiple personality disorder” because the new name emphasises the disruption of a person’s identity that characterises the disorder, while the term dissociation draws attention to the actual mental process taking place. When under the control of one identity, (i.e. when those aspects of self are in the conscious foreground), the person is usually unable to remember some of the events that occurred while other personalities were in control. The different identities, referred to as alters, can develop so independently of one another that they exhibit differences in speech, mannerisms, attitudes, thoughts, and gender orientation. The alters may differ in “physical” properties such as allergies, right-or-left handedness, or even the need for eye glass prescriptions. The differences are distinct and can often be quite striking to the observer (Haddock, 2001).

where "Haddock, 2001" is The dissociative identity disorder resource book [sic sourcebook].

  • 1
    Thank you! The second to last sentence in that quote looks promising. However, I don't yet see how that book is relevant: google's search comes up empty for either of "allergy", "allergies", "handed" and "handedness". I currently don't have access to the full text, so I may be missing something.
    – Saibot
    Oct 2, 2019 at 18:47

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