POWER OF ATTORNEY

        Know all by these presents, that the undersigned hereby constitutes and
appoints Joshua Brumm, signing singly, the undersigned's true and lawful
attorney-in-fact to:

        (1)    execute for and on behalf of the undersigned, in the
               undersigned's capacity as an officer and/or director of Kaleido
               Biosciences, Inc. (the "Company"), (i) Form ID, including any
               attached documents, to effect the assignment of codes to the
               undersigned to be used in the transmission of information to the
               United States Securities and Exchange Commission using the EDGAR
               System, (ii) Forms 3, 4 and 5, (iii) Schedule 13D, (iv) Schedule
               13G and (v) amendments of each thereof, in accordance with
               Section 16(a) of the Securities Exchange Act of 1934, as amended,
               and the rules thereunder;

        (2)    do and perform any and all acts for and on behalf of the
               undersigned which may be necessary or desirable to complete and
               execute any such Form 3, 4 or 5, Schedule 13D. Schedule 13G or
               any amendments thereto and timely file such form with the United
               States Securities and Exchange Commission and any stock exchange
               or similar authority; and

        (3)    take any other action of any type whatsoever in connection with
               the foregoing which, in the opinion of such attorney-in-fact, may
               be of benefit to, in the best interest of, or legally required
               by, the undersigned, it being understood that the documents
               executed by such attorney-in-fact on behalf of the undersigned
               pursuant to this Power of Attorney shall be in such form and
               shall contain such terms and conditions as such attorney-in-fact
               may approve in such attorney-in-fact's discretion.

        The undersigned hereby grants to each such attorney-in-fact full power
and authority to do and perform any and every act and thing whatsoever
requisite, necessary, or proper to be done in the exercise of any of the rights
and powers herein granted, as fully to all intents and purposes as the
undersigned might or could do if personally present, with full power of
substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's substitute or substitutes, shall
lawfully do or cause to be done by virtue of this Power of Attorney and the
rights and powers herein granted. The undersigned acknowledges that the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming, any of the
undersigned's responsibilities to comply with Section 16 or Regulation 13D-G of
the Securities Exchange Act of 1934, as amended. The undersigned hereby agrees
to indemnify the attorney-in-fact and the Company from and against any demand,
damage, loss, cost or expense arising from any false or misleading information
provided by the undersigned to the attorney-in-fact.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in-fact.  This Power of Attorney may be filed with the
United States Securities and Exchange Commission as a confirming statement of
the authority granted herein. This Power of Attorney supersedes any prior power
of attorney in connection with the undersigned's capacity as an officer and/or
director of the Company.  This Power of Attorney shall expire as to any
individual attorney-in-fact if such attorney-in-fact ceases to be an executive
officer of the Company.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of February 27, 2019.

                                        /s/ Alison Lawton
                                        -----------------
                                        Name: Alison Lawton