[REVIEW] TIAM My Signature C Source

Tiam My Signature C Source Review:

I have, for nearly 2 years now, been incorporating a vitamin C serum in both my daily and nightly skincare routine. However, the serum(s) that I used only contained a 5% maximum concentration of vitamin C and it was quite expensive for a small amount. I did more research in the blogosphere and finally decided to give this much talked about serum a shot. This baby here contains a 20% concentration of vitamin C and was much cheaper! You don’t have to tell me twice. On the day it arrived, I started using it and have been very happy with the results.

This product used to be known as the O.S.T. C20 serum and Tiam (the company that produces the serum) is part of the Cosrx family. Now, I have a lot of faith in the entire Cosrx products line and so unsurprisingly, this blind faith extended to Tiam as well. I was not disappointed. This faint citrus scented serum has become my favourite part of my skincare routine, not only because I love the smell of oranges but mainly because it has actually helped lighten some of the scarring I had from blemishes around my chin area (the result of being a woman and suffering through hormonal blemishes during that time of the month).


– Regenerates the skin

– Brightens and balances skin tone

– Fades acne scars and lightens dark spots

– Exfoliates and removal of blackheads

– Anti-aging properties by tightening pores and reducing fine lines


Water, Ascorbic Acid, Alcohol, Sodium Lactate, Butylene Glycol, Glucose, PEG-60 Hydrogenated Castor Oil, 1, 2-Hexanediol, Phenoxyethanol, Sodium Hyaluronate, Bis-PEG-18 Methyl Ether Dimethyl Silane, Xanthan Gum, Diethoxyethyl Succinate, Ammonium Acryloyldimethyltaurate/VP Copolymer, Carthamus Tinctorius Flower Extract, Citrus Aurantium Dulcis, Glycerin, Zinc PCA, Panthenol, Niacinamide, t-Butyl Alcohol, Camellia Sinensis Leaf Extract, Beta-Glucan, Tocopheryl Acetate, Lecithin, Caprylic/Capric Triglyceride, Ubiquinone, Diisopropyl Adipate

Tiam My Signature C Source Review


Volume: 30ml

How to Use:

Once opened, it is advisable that you store this serum in a cool and dark place away from sunlight. The reason being that vitamin C is sensitive to light and if exposed too often can oxidise quickly. When this happens, the serum loses its effectiveness. Therefore, what I do is to store mine in the refrigerator, nestled nicely in between my bottle of ketchup and jar of olives.

I use this serum after applying my toner and with the dropper, I drop 5 drops on my face – forehead, cheeks, nose and chin. I massage this into my skin and a few seconds later will start to feel a tingling sensation, particularly around my jawline. Sometimes this feeling is bearable but sometimes it actually feels a little uncomfortable – like ant bites. I guess it depends on the condition of my skin on that day. The sensation, fortunately, does not last long and goes away after some massaging.

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After application, I wait approximately 20 minutes before continuing with my next skincare step as I want the serum to absorb fully into my skin and not have its effects cancelled out by the subsequent products I apply. As a result of this waiting time, I normally apply this serum only at night as I believe in both beauty products AND beauty sleep – I would much rather spend the 20 minutes in the morning under my duvet….ZzzzZZZzz.

For users with sensitive skin or maybe if it is your first time using a vitamin C serum, it is suggested that you mix this serum with a toner to dilute the effect as otherwise it may be deemed too harsh for your skin.

Also, if this is not already incorporated into your routine….Sunscreen! This is even more important if you are going to use this serum daily. I always make sure I slap on the sunscreen before leaving the house the next day. This is so even on days when the weather is overcast and the sun is hidden behind a cluster of thick grey clouds.

My Skin type: Oily / Combination: Oily T-zone, Dry U-zone; sensitive skin

Tiam My Signature C Source Review:

The serum comes housed in a see through dark brown glass bottle so I can easily tell how much is remaining. The dropper also works fine and picks up a generous amount of serum with one squeeze of the tip. My only gripe is the storage of this serum as I do find it quite annoying having to make a detour to the kitchen fridge just to apply this serum.

The first few months of using this serum I was in love with everything about it. From the citrusy smell to the tingling I felt each time I applied it. I figured that since it was tingling and as there were no resulting rashes on my skin, it must be working its magic.

Lo and behold, a month or so after religiously applying it in the night, I started to see improvements around my chin area. I have the misfortune of suffering from occasional hormonal blemishes on the chin and to compound this misfortune, I have the tendency to squeeze them. As a result, it leaves a mark even after the zit has healed.

This serum definitely helped to lighten the skin on my chin. However, the weird thing is lately, I notice that it has stopped working its magic. I no longer feel the tingling sensation when I apply it and I do not see a marked difference in the marks around my chin.

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Tiam My Signature C Source Review

I checked the colour of the serum and it is still a transparent liquid (apparently, if the serum turns a darker shade of amber / orange, it has oxidised and is no longer as effective) so I am not sure what happened to it. I deduced that potentially, this could be due to my frequent opening of the refrigerator in my eternal quest for food.

Probably each time I opened the fridge door, it reduced the effectiveness of the serum a little. For my next bottle (yes, I will repurchase), I will probably store the bottle in its box in the fridge. Talk about overkill!

Despite the decrease in effectiveness, everything else remains the same. The serum has a sticky consistency when applied on the face and will require some patting to help it absorb better. It has some slip to it and spreads easily on the skin.

Tiam My Signature C Source Review

After application, I wait for a good 20 minutes before I apply my Cosrx acids. However, during that waiting time, I can feel my skin start to tighten just a little – a gentle reminder to apply a moisturizer. To me, this indicates that the supposed moisturizing properties of this serum probably has a minimal impact on me.

Tiam My Signature C Source Review

As mentioned this serum has a faint orange scent but not to worry as it fades rapidly so you will not be able to fool yourself into thinking you’re in the Mediterranean even if you wanted to.

This vitamin C serum was effective for the first two months or so as I saw a distinct lightening of the scars left behind from the blemishes on my chin. However, proper storage is vital with this serum as it oxidises rather quickly, hence causing it to lose some of its effectiveness.

Its price is also perfect for the cost conscious as it is about £11 for a 20% concentration of vitamin C. I would definitely repurchase as I was happy with the results of the serum.

Where to buy:

eBay | Cosmetic-love

Have you tried Tiam My Signature C Source?

Do share your thoughts in comments 🙂

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6 thoughts on “[REVIEW] TIAM My Signature C Source”

  1. Hi…i have a sentive oily and acne prone skin Akso with uneven skin tone.I have never used any vit c serums. As this one’s concentration is 20% I’m bit afraid to apply thinking it would irritate my skin.So what would you suggest ? You mentioned people with sensitive skin should use a toner.what kind of toner ? Should we mix the toner with serum and then have to apply. Tia

  2. Hi Teena,

    Yes, if you have sensitive skin it is advisable you mix the serum with a toner that probably doesn’t contain any niacinamide. So most of the Innisfree toners / skins would be ok but do double check the ingredients first. Though, I am quite sure the Orchid range I currently use from Innisfree does not contain any.

    Mixing the serum I read will dilute the effect and as your skin gets used to it then you can slowly introduce the serum directly to your skin.


  3. Hi Sya,

    This serum is more water-based as it is quite runny and after applying it I usually wash my hands (before using the next serum) and there is no oily residue whatsoever on my palms.



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