Sales
Net sales for the three months ended September 30, 2021, were $48.0 million, an increase of 23.8%, as compared to $38.8 million for the same period in 2020. This growth was largely driven by double-digit increases across all sales channels, led by our DTC subscription sales of $6.2 million, up 41.4%, followed by our professional/B2B sales which grew $5.6 million, or 23.3%. Our subscription sales continue to be a key indicator of our growth strategy, our marketing success, and our ability to retain our customers. They also strengthen our brand loyalty.
Net sales for the nine months ended September 30, 2021, were $135.4 million, an increase of 32.4%, as compared to $102.3 million for the same period in 2020. This growth was largely driven by double-digit increases across all sales channels, led by professional/B2B sales which grew $19.7 million, or 32.5% growth, to $80.6 million year-to-date, as compared to $60.9 million for the same period in 2020. The Company’s DTC sales were $54.8 million in the nine months ended September 30, 2021, an increase of 32.2%, as compared to $41.4 million for same period in 2020. DTC subscription sales grew $5.2 million, or 43.4%, to $17.3 million in the nine months ended September 30, 2021, as compared to $12.0 million for same period in 2020.
Cost of Sales and Gross Profit
Cost of sales for the third quarter 2021 was $22.5 million, an increase of 15.6%, compared to $19.4 million for the third quarter of 2020. This increase in cost of sales was primarily driven by a 23.8% increase in net sales during the third quarter 2021.
Gross profit for the third quarter was $25.5 million, an increase of 32.1%, compared to $19.3 million for the same period in 2020. Gross profit as a percentage of sales for the third quarter of 2021 increased by 335 basis points, to 53.2%, compared to 49.9% during the same period of 2020.
Cost of sales for the nine-month period ended September 30, 2021, was $63.7 million, an increase of 16.0%, compared to $54.9 million for the third quarter of 2020. This increase in cost of sales was primarily due to increased product demand, reflected in the 32.4% sales increase during the nine-month period ended September 30, 2021.
Gross profit for the nine-month period ended September 30, 2021, was $71.7 million, an increase of 51.3%, compared to $47.4 million for the same period in 2020. Gross profit as a percentage of sales for the nine-months ended September 30, 2021, increased by 662 basis points, to 52.9%, compared to 46.3% during the same period of 2020.
Selling, General and Administrative Expenses
Total selling, general and administrative expenses for the third quarter of 2021 were $24.2 million, an increase of 79.7%, as compared to $13.5 million for the third quarter of 2020. This increase was primarily due to planned increases in marketing spend during the quarter of $10.8 million, up $8.4 million from $2.4 million during the third quarter of 2020. Excluding marketing expense, selling, general and administrative expenses were 28.0% of net sales during the third quarter of 2021 and 28.5% of sales during the same period in 2020. Research and development expense for the third quarter of 2021 was $2.2 million, as compared to $0.6 million for the third quarter of 2020.
Total selling, general and administrative expenses for the nine-month period ended September 30, 2021, were $57.1 million, an increase of 32.7%, as compared to $43.0 million for the same period in 2020. This increase was primarily due to planned increases in marketing spend during the period of $20.1 million, up $13.9 million from $6.1 million during the nine-month period ended September 30, 2020. Excluding marketing expense, selling, general and administrative expenses were 27.3% of net sales during the nine-month period ended September 30, 2021, and 36.0% of sales during the same period in 2020. Research and development expense for the nine-month period ended September 30, 2021, was $4.3 million, as compared to $3.1 million for the same period in 2020.