STALLERGENES : 1st Quarter 2010 : Sustained 13% Growth

ANTONY, France, April 15, 2010 -

    EURm                   2009     09/08     2010     10/09
                       EURm  %Sales Var.% EURm  %Sales Var.%
    Southern Europe    41.8      74    10 46.9      74    12
    (1)
    Other EU countries 12.7      23    36 14.6      23    15
    Other markets       1.7       3     0  1.8       3     8

    SLIT               47.2      84    16 55.0      87    17
    SCIT                6.9      12    11  6.3      10    (8)
    Other products      2.1       4    11  2.0       3    (6)

    Total Q1 sales     56.2     100    15 63.3     100    13

Sales

Consolidated sales for the 1st quarter grew by 13% to EUR 63.3
million (up 15% in 2009). Foreign exchange effects were positive by EUR 0.3
million.

This growth confirms the supremacy of SLIT over SCIT,
respectively posting growth of 17% and a decline of 8% over the 1st quarter.
SLIT now accounts for 87% of the laboratory's sales.

The analysis by geographic region highlights satisfactory
growth in all markets, with the "Other EU countries" region continuing to
drive Group growth under the effect of the significant increase in Oralair(R)
sales in Germany.

Changes in financial position and significant transactions and
events of the quarter

The financial position improved: cash net of debt was largely positive at
31 March, whereas it was negative at the same time last year.

Preliminary results of the Oralair(R) grasses trial in the US
should be obtained and released before the end of April.

Outlook for the current financial year

The good first quarter results confirmed the guidance for
full-year sales growth in excess of 8%, featuring further improvement in
profit margins.

About Stallergenes

Stallergenes is a European biopharmaceutical laboratory
specialising in treatments by immunotherapy for the prevention and treatment
of allergy-related respiratory conditions, such as rhino conjunctivitis,
rhinitis and allergic asthma. Stallergenes is ranked seventh among French
pharmaceutical laboratories. A pioneer and a leader in immunotherapy
treatments by sublingual administration, Stallergenes dedicates more than 20%
(gross) of its sales to its Research and Development activities, which are
primarily directed at developing a new therapeutic range enabling the
provision of immunotherapy treatments by sublingual tablets.

Stallergenes realised 2009 sales of EUR 193 million, with over
500,000 patients treated with Stallergenes desensitisation products.

    Euronext Paris (Compartment B).
    SBF 120 index.
    ISIN code: FR0000065674
    Reuters code: GEN.PA
    Bloomberg code: GEN.FP

For further financial information, please visit our website:
www.stallergenes.com

Contacts: Albert Saporta, Chairman and CEO, Tel. +33-1-55-59-20-04, Christian Thiry, Chief Financial Officer, Tel. +33-1-55-59-20-95, e-mail: investorrelations at stallergenes.fr; Investor and Analyst Relations: Lucile de Fraguier, Pavie Finance, Tel. +33-1-42-15-04-39, e-mail: contact at pavie-finance.com; Stallergenes Press Relations: Lise Lemonnier, Communication Officer, Tel. +33-1-55-59-20-96, e-mail: llemonnier at stallergenes.fr