Sienna Biopharmaceuticals, Inc.

			Power of Attorney

    Know all by these presents, that the undersigned hereby
constitutes and appoints each of (i) the Chief Executive Officer
of Sienna Biopharmaceuticals, Inc., a Delaware corporation (the
"Company"), who is currently Frederick C. Beddingfield III, (ii)
the Company's Chief Financial Officer, who is currently John W.
Smither, and (iii) the Company's General Counsel, who is
currently Timothy K. Andrews, and their respective successors
(including anyone serving in such capacities on an interim or
acting basis), signing singly, with full powers of substitution,
as the undersigned's true and lawful attorney-in-fact to:


1.   prepare, execute in the undersigned's name and on the
     undersigned's behalf, and submit to the U.S. Securities and
     Exchange Commission (the "SEC") a Form ID, including
     amendments thereto, and any other documents necessary or
     appropriate to obtain codes and passwords enabling the
     undersigned to make electronic filings with the SEC of
     reports required by Section 16(a) of the Securities
     Exchange Act of 1934 or any rule or regulation of the SEC;


2.   execute for and on behalf of the undersigned, in the
     undersigned's capacity as an officer and/or director of the
     Company, Forms 3, 4, and 5 and any amendments thereto in
     accordance with Section 16(a) of the Securities Exchange
     Act of 1934 and the rules thereunder;


3.   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, complete and execute
     any amendment or amendments thereto, and timely file such
     form with the SEC and any stock exchange or similar
     authority; and


4.   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
of the Securities Exchange Act of 1934.


    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.


    IN WITNESS WHEREOF, the undersigned has caused this Power
of Attorney to be executed as of this 16th day of April, 2018.

				/s/ John W. Smither
				By: John W. Smither