Ann Dermatol.  2018 Aug;30(4):458-461. 10.5021/ad.2018.30.4.458.

Intradermal Injection of Botulinum Toxin: A Safer Treatment Modality for Forehead Wrinkles

  • 1Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
  • 2Department of Medical Device Management & Research, SAIHST, Sungkyunkwan University, Seoul, Korea.
  • 3Yemiwon Dermatologic Clinic, Seoul, Korea.


Intramuscular injection of botulinum toxin A (BTXA) is commonly used for the treatment of forehead wrinkles. In practice, physicians often use an intradermal injection for this purpose, as they feel that there is a lower risk of adverse effects compared with intramuscular injection. However, there are no direct comparative studies between those two injection modalities. We conducted a 24-week long, double-blinded, split-face, pilot study of three participants to compare the efficacy and safety of intradermal or intramuscular injection of BTXA for the treatment of forehead wrinkles. Maximum improvement of wrinkles and the time to achieve maximum effect were similar for both methods. The brow level was lower on the intramuscular injection side throughout the follow-up period for all participants. Subjective satisfaction with wrinkles was similar on both sides, but patients felt more heaviness of the eyebrow on the intramuscular side. No serious side effects were noted. In conclusion, the anti-wrinkle effect of BTXA was not significantly different between intramuscular and intradermal injections. However, side effects such as eyebrow ptosis, and heaviness were more prominent after intramuscular injection.


Botulinum toxins; Forehead; Intradermal injections

MeSH Terms

Botulinum Toxins*
Follow-Up Studies
Injections, Intradermal*
Injections, Intramuscular
Pilot Projects
Botulinum Toxins


  • Fig. 1 (A) Photograph of Patient 1 with forced upward gaze before injection. The brow to hairline length was measured at the mid-pupillary level (a blue line denoted as ⓐ) and the inner epicanthus level (a yellow line denoted as ⓑ) on either sides. Blue dots represent intradermal injection sites and red dots represent intramuscular injection sites. (B) Four weeks after the injection of Patient 1. The brow to hairline length at week 4 was measured at the mid-pupillary level (a blue line denoted as ⓒ) and the inner epicanthus level (a yellow line denoted as ⓓ). The difference in the brow to hairline length before injection and after injection (in this case, ⓐ – ⓒfor mid-pupillary level, and ⓑ – ⓓfor inner epicanthus level) was defined as brow ptosis.

  • Fig. 2 Wrinkle scores of Patients 1, 2, and 3. The blue line is the wrinkle score of the intradermally injected side (ID). The orange line is the wrinkle score of the intramuscularly injected side (IM). Patient 1: 52 years (female), Patient 2: 71 years (female), Patient 3: 56 years (female).

  • Fig. 3 Brow ptosis of Patients (Pt) 1, 2, and 3 at the mid-pupillary level and the inner epicanthus level. The blue line shows brow ptosis on the intradermally injected side (ID). The orange line shows brow ptosis on the intramuscularly injected side (IM). The difference in the brow to hairline lengths were measured in centimeters.

  • Fig. 4 (A) Pretreatment photograph of Patient 2 with forced upward gaze. (B) One week after injection in Patient 2. The right side (Rt) was the intradermal injection side and the left side (Lt) was the intramuscular injection side. Eyebrow ptosis is more prominent at the mid-to inner eyebrow on the intramuscular side, and this looks like “samurai eyebrow” when the patient attempted an upward gaze (arrows).


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