In-Depth Comparison: Rapidlash and Lashfridays Lash Serum.

In-Depth Comparison: Rapidlash and Lashfridays Lash Serum.

Rapidlash and Lashfridays stand tall among the well-regarded lash growth serums, each having received thousands of positive reviews and testimonials applauding their lash-amplifying effectiveness. That being said, certain distinctions between Rapidlash and our lash serum deserve our attention.

This article provides an impartial assessment comparing Rapidlash and Lashfridays, discussing essential factors like customer reviews, ingredients, costs, and possible adverse reactions. Please bear in mind that the information provided specifically pertains to the version of Rapidlash available in the United States.

What Are Eyelash Serums

Lash serum

Eyelash serums are liquid formulas that enhance the natural growth cycles of lashes and make them appear thicker and longer. They stimulates the lashes in their growing phase and protects them from breakage while strengthening their roots. When applied daily, these lash serums make the eyelash appear fuller, stronger, and longer. 

What Type of Lash Serum Are Rapidlash and Lashfridays?

The main two types of lash serums are prostaglandin-based lash serums and peptide-based lash serums. Rapidlash is a prostaglandin-based lash serum and Lashfridays is a peptide-based lash serum.


RAPIDLASH: Prostaglandin

Prostaglandin-based lash serums contain hormones that can extend the duration of the growth phases of lashes. Similar to Grandelash, Rapidlash is a prostaglandin based lash serum containing Isopropyl Cloprostenate - a synthetic version of prostaglandin.

Prostaglandins are a group of naturally occurring lipids (fats) found in many parts of the body and are involved in a variety of biological processes.

Isopropyl Cloprostenate, specifically, is often used in eyelash growth serums due to its potential to stimulate the growth of eyelashes. It is believed to extend the growth phase of the eyelash hair cycle, leading to longer, thicker, and darker lashes.

Isopropyl Cloprostenate is structurally similar to the active ingredient (Bimatoprost) in a glaucoma medication called Lumigan, developed by Allergan. Doctors and patients noticed that Lumigan, when used to treat glaucoma, had a side effect of causing significant eyelash growth. This led Allergan to develop and market a new product called Latisse, using the same active ingredient but specifically for the purpose of promoting eyelash growth.

While Isopropyl Cloprostenate is a different compound than Bimatoprost, it's used in a similar way in some non-prescription eyelash growth products

How Does Isopropyl Cloprostenate work?

Now that we know what Isopropyl Cloprostenate is, let’s find how it works.

  • Isopropyl Cloprostenate is believed to influence the growth cycle of eyelashes. More specifically, it seems to increase the duration of the Anagen phase (the growth phase) of the eyelash hair cycle, leading to longer lashes.
  • This compound might also enhance the size of the dermal papilla – the part of the hair follicle where the hair actually grows. By doing so, it could potentially make the eyelashes thicker.
  • Isopropyl Cloprostenate may stimulate the pigment cells (melanocytes) in the hair follicles, leading to darker lashes.



Peptides are chains of Amino acids. You might have heard about the importance of amino acids as these acids are the supporting and building bricks of protein chains in the human body. A peptide lacks the number of amino acids compared to protein, so increasing peptides in the body leads to better hair health.

Peptides also help in Collagen building. Collagen is basically a massive particle but helps the skin and hair to get better. But since the size of the molecule is so large, it cannot get into the skin if applied topically.

Peptides having the same constituents and being smaller in size can very well penetrate the skin and enhance the health of eyelashes. The other two proteins essential for hair and skin health are elastin and keratin, which have peptides. This is why peptides are so crucial for eyelash enhancement.

How Does The Peptide Compound Work?

The peptide serum provides the most significant peptide amino chain to the hair to strengthen it in its growth and after-growth phase.

  • The basic peptide found in lashfridays is Myristoyl Pentapeptide-17. This compound is a highly performing constituent that hydrates the peptides and makes them appear healthier, thick, and shiny. It fortifies and rejuvenates the life of eyelashes, which intensifies the results.
  • The peptide called Acetyl Tetrapeptide-3 aids in building stronger and fuller eyelashes and helps protect them from damage and breakage due to dryness. This peptide has proven to increase the strength of roots and thickness of lashes.

Other Ingredients

Lash Serum

Aside from their main active ingredients, Rapidlash and Lashfridays have the following key ingredients in their serums.


  • Octapeptide-2: Octapeptide-2 is a peptide that is believed to stimulate hair growth by strengthening the hair follicle.
  • Copper Tripeptide-1: This ingredient is a peptide that is known to stimulate hair growth and has anti-inflammatory properties.
  • Biotin: Biotin, also known as Vitamin B7, is known to strengthen hair and promote its growth.
  • Panthenol: Also known as Pro-Vitamin B5, panthenol is a humectant, meaning it helps retain moisture. This can make eyelashes more flexible and less likely to break.
  • Glycine Soja (Soybean) Oil: This oil is often used in cosmetics for its moisturizing properties.
  • Cucurbita Pepo Pumpkin Seed Extract  This extract is believed to stimulate hair growth.
  • Sodium Hyaluronate: This is the sodium salt of hyaluronic acid, which is a powerful hydrating ingredient that can hold up to 1,000 times its weight in water.


  • Purified water - Water is used as a solvent to dissolve the serum ingredients.
  • Hyaluronic Acid - Hyaluronic Acid is also used to thicken the lash serum.
  • Collagen - Collagen enhances the appearance and feel of lashes by increasing lash body, suppleness and sheen.
  • Cucurbita Pepo Pumpkin Seed Extract - The oil from pumpkin seeds helps increase hair growth.
  • Sphingolipids - Sphingolipids are complex, long chain lipids (fats) that function as conditioning ingredients.
  • Arginine - Amino acids that help condition lash hair.
  • Biotin (Vitamin B7) - Biotin adds body and shine to lash hair.
  • Keratin - Keratin is a type of protein that works by smoothing down the cells that overlap to form your lash hairs. This can make them smoother.

      What are the potential side effects of Rapidlash and Lashfridays?

      Side Effects Lash Serum

      Potential Side Effects of Rapidlash

      Known potential side effects of prostaglandin analog lash serums include:

      • Eye pruritus - dry, itchy eyes.
      • Conjunctival hyperemia - redness of the eyes.
      • Lash loss/fall
      • Skin hyperpigmentation

      Less common side effects include:

      • Pigmentation of the iris. Any Iris pigmentation is likely to be permanent and my not be noticeable for several months or years.
      • Lid pigmentation. Eyelid pigmentation has been reported although this has been reported as reversable when use is stopped.
      • Hair growth outside the treatment area. 

      There may also be a risk of Enophthalmos  - shrinkage of fat around the eye, causing the eye to become sunken in.

      Due to concerns about the side effects risk of prostaglandins any serums containing the prostaglandin hormone, are banned from direct sale in Canada and Australia  and require a prescription in many countries.

      Potential Side effects of Lashfridays

      The side effects from the ingredients in Lashfridays are limited. According to a recent study of a lash serum containing Myristoyl Pentapeptide-17, a key ingredient of Lashfridays, 6% of participants experienced temporary redness and irritation of the eyes.

      Reviews of Rapidlash and Lashfridays

      Rapidlash Reviews

      Rapidlash on the website influenster has an average rating of 4.3/5 from 1,300 reviews. Reviewers commonly refer to the product helping with lash length and lash thickness as well as rapid results.

      "I use this every night, and have noticed a significant difference with my lashes. I really like how it helped make my lashes grow thicker and more full." - Brooke B. 5/5

      Lashfridays Reviews

      Before After Lash Serum

      Lashfridays lash serum currently has an average rating of 4.4/5  from approximately 1m300 reviews. The most common benefits mentioned in the reviews refer to lashfridays helping with lash growth and lash thickness.

      "Have been using lash Friday’s lash and brow serum for 4 weeks now. Can noticeably see a difference in length and thickness of lashes and my brows are starting to fill in." - Caroline M. 5/5

      How much does Rapidlash and Lashfridays cost?


      Rapidlash Cost

      Rapidlash costs USD $49.95 for 3 months supply. This works out at USD $ 0.55 per application. 

      Lashfridays Cost

      Lashfridays costs USD $39 for 3 months supply. This works out at USD $ 0.43 per application. If a twin pack is purchased for USD $59.99 it works out at USD $0.32 per application.


      Below is a summary of the key differences between Rapidlash and Lashfridays breaking down by price, reviews, side effects and key ingredient. If you would like to try lashfridays lash serum yourself click here.


      Features RapidLash Lashfridays
      Type of Serum Prostaglandin-based (Isopropyl Cloprostenate) Peptide-based
      Key Ingredients Octapeptide-2, Copper Tripeptide-1, Biotin, Panthenol, Soybean Oil, Pumpkin Seed Extract, Sodium Hyaluronate Purified Water, Hyaluronic Acid, Collagen, Pumpkin Seed Extract, Sphingolipids, Arginine, Biotin, Keratin
      Potential Side Effects Eye pruritus, Conjunctival hyperemia, Skin hyperpigmentation, Iris pigmentation, Eyelid pigmentation, Hair growth outside treatment area, Enophthalmos Temporary redness and irritation of the eyes
      Rating 4.3/5 4.4/5
      Cost for 3 months supply USD $49.95 (USD $0.55 per application) USD $39 (USD $0.43 per application); Twin pack for USD $59.99 (USD $0.32 per application)
      Reviewer Comment "I use this every night, and have noticed a significant difference with my lashes. I really like how it helped make my lashes grow thicker and more full." - Brooke B. 5/5 "Have been using lash Friday’s lash and brow serum for 4 weeks now. Can noticeably see a difference in length and thickness of lashes and my brows are starting to fill in." - Caroline M. 5/5