Not too sure though. But If' the make up is bought from any of the concessions brand within Debenhams, you can't earn the £10 gift card.

For everyone.

Looking at the terms and conditions - looks like a no - point 8

Great giftcard giveaway - T&Cs
1. Customers who make in store purchases of £50 or more in one transaction in store in the UK between Monday 16 November 2015 to Sunday 29 November 2015 (inclusive) will qualify for a £10 promotional gift card (“Promotional Gift Card”). Promotional Gift Cards are subject to availability whilst stocks last.
2. A maximum of one Promotional Gift Card may be issued per customer per day, when a customer is spending £50 or more in one transaction. For the avoidance of doubt, two or more qualifying transactions by the same customer in the same day will only result in one Promotional Gift Card being issued.
3. The Promotional Gift Card can only redeemed on purchases made in store in the UK but cannot be redeemed on http://www.Debenhams.com, the Debenhams in-store kiosks and any Debenhams apps, or for telephone orders.
4. The Promotional Gift Card will be valid to be redeemed in store only from Monday 30 November 2015 – Thursday 24 December 2015 (inclusive).
5. Only one Promotional Gift Card may be redeemed per transaction.
6. No change will be given for use of the Promotional Gift Card on purchases under £10.
7. Customers will not qualify for a Promotional Gift Card if redeeming a reward voucher, account voucher or other promotional voucher or promotional code.
8. Purchases and top ups of gift cards, gift vouchers and e-cards will not qualify for a Promotional Gift Card.
9. If items are subsequently returned then Debenhams reserve the right to request the Promotional Gift Card be returned or reduce the value of the refund by £10.
10. The Promotional Gift Card cannot be earned or redeemed with any of the concessions trading within Debenhams.
11. The Promotional Gift Card cannot be earned or redeemed in any of restaurants or cafés, including Costa.
12. Staff are not permitted to earn or redeem a Promotional Gift Card. The Promotional Gift Card cannot be used in conjunction with a staff discount card.
13. The Promotional Gift Card cannot be topped up. All money remaining on the card will expire on Friday 25 December 2015.
14. The Promotional Gift Card may not be exchanged for cash or vouchers, used as a deposit on a credit agreement, used to settle a Debenhams Account Card or to purchase financial or travel services (including gift cards).
15. The Promotional Gift Card should be treated in the same way as cash. We are unable to replace the Promotional Gift Card if it is lost, damaged or stolen.
16. The Promotional Gift Card remains the property of Debenhams. Debenhams reserves the right to reject any Promotional Gift Card that it deems in its sole discretion is illegible or incomplete or has been forged, defaced or otherwise tampered with. Photocopies or other reproductions of the Promotional Gift Card will not be valid.
17. Debenhams reserve the right to amend these terms and conditions from time to time where it reasonably considers it necessary to do so (for example, to change the scope of the gift card service, notify of the service’s withdrawal or in the event of circumstances beyond its control). Reasonable notice of such changes will be given and will be available at http://www.debenhams.com/customer-service/terms-and-conditions.
18. Promoter – Debenhams Retail PLC, registered office at 10 Brock Street, Regent’s Place, London, NW1 3FG, registered number 00083395.
19. These terms and conditions are governed in accordance with the laws of England and Wales.

They didn't specify .They just said when you spend £50 +.You may ask instore.